Folded ultrasonic end effectors with increased active length

ABSTRACT

An end effector for use with an ultrasonic surgical instrument. A body extends along a longitudinal axis. The body includes a proximal end and a distal end. The body comprises an outer surface that defines an inner portion. The proximal end of the body is configured to couple to an ultrasonic transducer configured to produce vibrations at a predetermined frequency and a predetermined amplitude. A folded element includes a first end coupled to the distal end of the body and extending proximally along the longitudinal axis from the distal end of the body toward the proximal end of the body. The folded element comprises a second free acoustic end. The folded element and the outer surface of the body define a single substantially parallel acoustic path. A clamp arm is operatively coupled to the body.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application, under 35 USC §121, of U.S.patent application Ser. No. 11/998,758, filed Nov. 30, 2007, entitledFOLDED ULTRASONIC END EFFECTORS WITH INCREASED ACTIVE LENGTH, now UnitedStates Patent Publication Number 2009/0143796.

BACKGROUND

Ultrasonic instruments, including both hollow core and solid coreelements, are used for the safe and effective treatment of many medicalconditions. Ultrasonic instruments, and particularly ultrasonicinstruments comprising contact ultrasonic elements, are advantageousbecause they may be used to cut and/or coagulate tissue using energy inthe form of mechanical vibrations transmitted to a surgical end effectorat ultrasonic frequencies. Ultrasonic instruments utilizing contactultrasonic elements are particularly advantageous because of the amountof ultrasonic energy that may be transmitted from an ultrasonictransducer, through a transmission component or waveguide, to thesurgical end effector. Such instruments may be used for open orminimally invasive surgical procedures, such as endoscopic orlaparoscopic surgical procedures, wherein the end effector is passedthrough a trocar to reach the surgical site.

Activating or exciting a single or multiple-element end effector of suchinstruments at ultrasonic frequencies induces longitudinal, transverseor torsional vibratory movement relative to the transmission componentthat generates localized heat within adjacent tissue, facilitating bothcutting and coagulating. Because of the nature of ultrasonicinstruments, a particular ultrasonically actuated end effector may bedesigned to perform numerous functions. Ultrasonic vibrations, whentransmitted to organic tissue at suitable energy levels using a suitableend effector, may be used to cut, dissect, separate, lift, transect,elevate, coagulate or cauterize tissue, or to separate or scrape muscletissue away from bone with or without the assistance of a clampingassembly.

Ultrasonic vibration is induced in the surgical end effector byelectrically exciting a transducer, for example. The transducer may beconstructed of one or more piezoelectric or magnetostrictive elementslocated in the instrument hand piece. Vibrations generated by thetransducer section are transmitted to the surgical end effector via anultrasonic transmission component such as a waveguide extending from thetransducer section to the surgical end effector. The waveguide and endeffector are most preferably designed to resonate at the same frequencyas the transducer. Therefore, when an end effector is attached to atransducer the overall system frequency is the same frequency as thetransducer itself.

The zero-to-peak amplitude of the longitudinal ultrasonic vibration atthe tip, d, of the end effector behaves as a simple sinusoid at theresonant frequency as given by:

d=A(x)sin(ωt)  (1)

where:

ω=the radian frequency which equals 2π times the cyclic frequency, f;and

A(x)=the zero-to-peak amplitude as a function of position x along theblade.

The longitudinal excursion is defined as the peak-to-peak (p-t-p)amplitude, which is just twice the amplitude of the sine wave or 2A.A(x) varies as a standing wave pattern and is referred to as thedisplacement curve. At displacement nodes, A(x)=zero and there is noultrasonic excursion. At antinodes, A(x) is at a local extreme, either amaximum or a minimum (minimum refers to a negative maximum).

Acoustic assemblies may comprise acoustic horns geometrically formed toamplify, attenuate, or transmit the amplitude of the vibrations producedby the piezoelectric or magnetostrictive actuators. Conventional hornsgenerally have two distinct cross-sectional areas, usually with a taperbetween them, with the larger area, or input area, facing the actuationstack. Conventional horns are configured with a direct transitionbetween the input and output areas. An amplifying acoustic horn (e.g., afore-bell) is configured as a tapered solid with a larger diameter end(e.g., the input area) adapted to couple directly to the transducer anda smaller diameter end (e.g., the output area) at the tip adapted tocouple to the end effector. The tapering cross-sectional area of thehorn amplifies the limited displacements generated by the transducer.Vibration actuators operating from acoustic to ultrasonic frequenciesgenerally include three main components. These components include thehorn, a stack of piezoelectric or magnetostrictive elements (e.g., atransducer, actuator stack), and a backing material (e.g., an end-bell).The stack of piezoelectric elements is held in compression by a stressbolt that joins the backing material to the horn. The change in area isused to amplify the limited displacement that is induced by the stack.

Solid core ultrasonic instruments may be divided into single-element endeffector devices and multiple-element end effector devices.Single-element end effector devices include instruments such as blades,scalpels, hooks, or ball coagulators. Multiple-element end effectorsinclude the single-element end effector in conjunction with a mechanismto press or clamp tissue against the single-element end effector.Multiple-element end effectors comprise clamping scalpels, clampingcoagulators or any combination of a clamping assembly with asingle-element end effector generally referred to as clamp coagulators.Multiple-element end effectors may be employed when substantial pressuremay be necessary to effectively couple ultrasonic energy to the tissue.Such end effectors apply a compressive or biasing force to the tissue topromote faster cutting and coagulation of the tissue, particularly looseand unsupported tissue.

Various design examples of vibration amplifiers, e.g., acoustic horns,are discussed in “Novel Horn Designs for Ultrasonic/Sonic CleaningWelding, Soldering, Cutting and Drilling”, Proc. SPIE Smart StructuresConference, Vol. 4701, Paper No. 34, San Diego, Calif., March 2002.Additional examples of horn designs are discussed in United StatesPatent Application Publication US20040047485A1, titled “Folded Horns forVibration Actuator”. The first reference discusses a folded hornconnected to an ultrasonic transducer or actuator and the other end isin contact with the work piece (e.g., an ultrasonic blade or anultrasonic transmission component or waveguide coupled to the blade).The “distal end” of the folded horn described in the reference, however,is not in contact with the work piece.

There is a need, however, for an end effector comprising one or morefolded elements to reduce the overall length of an end effector whileremaining in contact with the target tissue. There is also a need for anend effector comprising moveable folded elements. There is also a needfor an end effector comprising a folded element located at the distalend that is located neither at a node nor an antinode and operates at anintermediate displacement amplitude.

SUMMARY

In one embodiment, an end effector for use with an ultrasonic surgicalinstrument comprising a body extending along a longitudinal axis. Thebody comprises a proximal end and a distal end. The body comprises anouter surface that defines an inner portion. The proximal end of thebody is configured to couple to an ultrasonic transducer configured toproduce vibrations at a predetermined frequency and a predeterminedamplitude. A folded element has a predetermined length. The foldedelement comprises a first end coupled to the distal end of the body andextending proximally along the longitudinal axis from the distal end ofthe body toward the proximal end of the body into the inner portion. Thefolded element comprises a second free acoustic end, wherein the foldedelement and the outer surface of the body define a single substantiallyparallel acoustic path. A clamp arm is operatively coupled to the body.

FIGURES

The novel features of the various embodiments are set forth withparticularity in the appended claims. The various embodiments, however,both as to organization and methods of operation, together withadvantages thereof, may best be understood by reference to the followingdescription, taken in conjunction with the accompanying drawings asfollows.

FIG. 1 illustrates one embodiment of an ultrasonic system comprising asingle-element end effector.

FIGS. 2 A-D illustrate one embodiment of an ultrasonic system comprisinga multi-element end effector.

FIG. 3 illustrates one embodiment of a connection union/joint for anultrasonic instrument.

FIG. 4 is a schematic diagram of one embodiment of a hollow tubular endeffector.

FIG. 4A is a longitudinal cross-sectional view of the end effector shownin FIG. 4.

FIG. 4B is a cross-sectional view of the end effector shown in FIG. 4taken along line 4B-4B.

FIG. 5 is a schematic diagram of one embodiment of an end effectorcomprising a folded element defining a parallel acoustic path.

FIG. 5A is a longitudinal cross-sectional view of the end effector shownin FIG. 5.

FIG. 5B is a cross-sectional view of the end effector shown in FIG. 5taken along line 5B-5B.

FIG. 6 illustrates a schematic diagram of one embodiment of an endeffector comprising a folded element defining a parallel acoustic path.

FIG. 6A is a longitudinal cross-sectional view of the end effector shownin FIG. 6.

FIG. 6B is a cross-sectional view of the end effector shown in FIG. 6taken along line 6B-6B.

FIG. 7 graphically illustrates a characteristic ultrasonic displacementcurve for an end effector shown in FIGS. 4, 4A, and 4B.

FIG. 8 graphically illustrates a characteristic ultrasonic displacementcurve for the end effectors shown in FIGS. 5, 5A, and 5B FIGS. 6, 6A,6B.

FIG. 9 illustrates a schematic diagram of one embodiment of amulti-element end effector comprising a folded element defining aparallel acoustic path.

FIG. 10 illustrates a schematic diagram of one embodiment of amulti-element end effector comprising a folded element defining aparallel acoustic path.

FIG. 11 illustrates a longitudinal cross-sectional view of oneembodiment of an extendable tubular end effector.

FIG. 12 illustrates a schematic diagram of one embodiment of a rotatableend effector.

FIG. 13 is a schematic diagram of a straight elongated end effector.

FIG. 14 is a schematic diagram of one embodiment of an effectorcomprising a folded element defining a parallel acoustic path.

FIG. 15 is a schematic diagram of one embodiment of an end effectorcomprising a folded element defining a parallel acoustic path.

FIG. 16 graphically illustrates a characteristic ultrasonic displacementcurve of the straight elongated end effector shown in FIG. 13.

FIG. 17 graphically illustrates a characteristic ultrasonic displacementcurve of one embodiment of an end effector comprising a folded elementdefining a parallel acoustic path shown in FIG. 14.

FIG. 18 is a schematic diagram of one embodiment of an end effectorcomprising a folded element defining a parallel acoustic path.

FIG. 18A is a cross-sectional view of the end effector shown in FIG. 18taken along line 18A-18A.

FIG. 19 graphically illustrates a characteristic ultrasonic displacementcurve of one embodiment of the end effector shown in FIGS. 18 and 18Acomprising a folded element defining a parallel acoustic path.

FIG. 20 illustrates one embodiment of a slotted end effector comprisinga folded element defining a parallel acoustic path.

FIG. 20A illustrates a cross-sectional view of the slotted end effectorshown in FIG. 20 taken along line 20A-20A.

FIGS. 21A-D illustrate one embodiment of a multi-element slotted endeffector comprising a folded element defining a parallel acoustic path.

DESCRIPTION

Before explaining the various embodiments in detail, it should be notedthat the embodiments are not limited in their application or use to thedetails of construction and arrangement of parts illustrated in thecontext of the accompanying drawings and description. The illustrativeembodiments may be implemented or incorporated in other embodiments,variations and modifications, and may be practiced or carried out invarious ways. For example, the surgical instruments and end effectorconfigurations disclosed below are illustrative only and not meant tolimit the scope or application thereof. Furthermore, unless otherwiseindicated, the terms and expressions employed herein have been chosenfor the purpose of describing the illustrative embodiments for theconvenience of the reader and are not limited in this context.

The various embodiments relate, in general, to ultrasonic surgical endeffectors for use in surgical instruments and, more particularly, toultrasonic surgical end effectors with improved elevating, cutting,and/or coagulation features, including, for example, improved bone andtissue removal, aspiration, and coagulation. An end effector may bestraight, curved, hollow, or solid, and may be useful for either open orlaparoscopic surgical procedures. An end effector according to thevarious embodiments described herein may be particularly useful inprocedures where it is desirable to cut and coagulate soft tissue andcontrol bleeding while simultaneously cutting tissue. An end effectoraccording to various embodiments may be useful in surgical spineprocedures, especially to assist in posterior access in removing muscleaway from bone. An end effector according to the various embodimentsdescribed herein may reduce the amount of force required by the user tocut tissue or to separate muscle away from bone and, in variousembodiments, may be useful to simultaneously hemostatically seal orcauterize the tissue. A variety of different end effector configurationsare disclosed and described.

Examples of ultrasonic surgical instruments are disclosed in U.S. Pat.Nos. 5,322,055 and 5,954,736 and in combination with ultrasonic bladesand surgical instruments disclosed in U.S. Pat. Nos. 6,309,400 B2,6,278,218B1, 6,283,981 B1, and 6,325,811 B1, for example, areincorporated herein by reference in their entirety. These referencesdisclose ultrasonic surgical instrument designs and blade designs wherea longitudinal mode of the blade is excited. Certain embodiments willnow be described to provide an overall understanding of the principlesof the structure, function, manufacture, and use of the devices andmethods disclosed herein. One or more examples of these embodiments areillustrated in the accompanying drawings. Those of ordinary skill in theart will understand that the devices and methods specifically describedherein and illustrated in the accompanying drawings are non-limitingembodiments and that the scope of the various embodiments is definedsolely by the claims. The features illustrated or described inconnection with one embodiment may be combined with the features of oneor more other embodiments. Modifications and variations of theillustrated embodiments are intended to be included within the scope ofthe claims.

Ultrasonic instruments are designed and manufactured such that themaximum amplitude of the longitudinal ultrasonic vibration occurs at anantinode, which is localized at or near the distal end of the endeffector to maximize the longitudinal excursion of the distal end. Theminimum amplitude of the longitudinal ultrasonic vibration occurs at anode. The active length of an ultrasonic instrument may be defined asthe distance from the distal end of the end effector (e.g., the locationof the antinode where ultrasonic displacement is at a maximum) to aproximal location along the end effector prior to the adjacent nodewhere the ultrasonic displacement decreases below a predetermined levelof 50%, for example. A nodal gap is a length of an end effector segmentsurrounding a node where ultrasonic displacement is below thepredetermined 50% level. Within the nodal gap, there is insufficientultrasonic displacement to generate the necessary heat for efficientand/or effective cutting and/or coagulating of tissue.

The relatively low displacements in the vicinity of the node result inlower amounts of heat being delivered to tissue in contact with the endeffector in a nodal gap region. In the nodal gap region, the tissue incontact with the end effector is not heated directly and is noteffectively cut and/or coagulated. Accordingly, the tissue may stick tothe end effector or may be desiccated without being transected. Thus, inultrasonic surgical instruments, there may be advantageous toeliminating the nodal gap and/or increasing the active length of the endeffector.

In conventional ultrasonic instruments, the active length of an endeffector is generally less than a quarter wavelength (λ/4). A quarterwavelength is primarily determined by the frequency and speed of soundin the end effector material. The speed of sound in most metals suitablefor ultrasonic components is approximately 5,000 meters per second. At55.5 kHz the wavelength is approximately 3.58 inches, and a quarter waveis about 0.886 inches (in Ti6Al4V the quarter wavelength is 0.866inches). The active length in titanium (Ti) is nominally 0.6 inches (≈15mm). While there are faster materials that provide longer activewavelengths, these materials are generally not suitable for surgicalinstruments.

Various embodiments of end effectors described herein comprise an activelength that is longer than a quarter wavelength and may be an integralmultiple of a quarter wavelength. The node (e.g., the location ofminimum or no displacement) may be located at the distal end of the endeffector that is presented to the patient. In such embodiments, theantinode (e.g., the location of maximum displacement) occurs somewherealong the longitudinal length of the end effector between a node and anantinode but not at the distal end. Moving away from the antinode, thedisplacement decreases to either side as the adjacent nodes areapproached. The active length may be a multiple of the nominal activelength.

As previously discussed, conventional ultrasonic instruments have anominal active length that is limited to about 15 mm. In conventionaldesigns, the active length is measured from the distal end (e.g.,location of an antinode and maximum displacement) of the end effector toa location where the displacement amplitude falls to 50% of the maximum.Because the location generally occurs before the first distal node isreached, the active length of conventional end effectors is generallyless than a quarter wavelength (λ/4).

In one embodiment, an ultrasonic instrument may comprise asingle-element end effector (e.g., a blade) coupled to an acousticwaveguide or horn element. The end effector may comprise one or more“folded elements” as described in more detail below. The fold portion ofthe folded element may be located at or in proximity to a node, anantinode, or may be located anywhere therebetween. A folded element maybe configured as a cutting and/or coagulating end effector with anactive region located at and/or in between the fold and the distal endof the folded element. An end effector comprising a folded elementaccording to the various embodiments discussed herein may comprise anactive length that is longer than the active length of a conventionalend effector without folded elements. The folded element also maycomprise non-cutting “dull” regions, which may be located at a fold nearthe distal end of the instrument. In one embodiment, the fold may belocated at or near a node. A fold located at a node remains a node,e.g., where ultrasonic displacement is zero, and provides a non-cutting“free-end” at the distal end of the end effector. The dull regionsremain dull even when the end effector is ultrasonically activated. Thismay be desirable in certain medical procedures where the distal end ofthe end effector is not necessarily used for cutting tissue. In oneembodiment, the fold may be located at or near an antinode. A foldlocated at or near an antinode remains an antinode, e.g., whereultrasonic displacement is maximum, and provides an active end forcutting and/or coagulating tissue that comes into contact therewith. Inother embodiments, a fold may be located between a node and an antinode.The displacement at a fold located between a node and an antinodedepends on whether the fold is located nearer to the node or theantinode. Accordingly, a desired displacement that is phased betweenzero and maximum may be realized by appropriately locating the foldbetween a node and antinode.

In another embodiment, an ultrasonic instrument may comprise amulti-element end effector (e.g., a blade and a clamping mechanism)coupled to an acoustic waveguide or horn element. The end effector maycomprise one or more “folded elements”. A clamp assembly is coupled tothe end effector at a distal end as described in more detail below. Theclamp assembly comprises a clamp arm and a single element end effector(e.g., a blade) to clamp tissue therebetween. As previously discussed,the fold may be located at or in proximity to a node, an antinode, ormay be phased anywhere therebetween. The folded element may beconfigured to cut and/or coagulate. The active region may be locatedanywhere between the fold and the distal end of the end effector and mayprovide a longer active length than a conventional end effector withoutfolded elements. Tissue may be received and squeezed between the endeffector and a clamp arm. Pressure may be applied to the tissue locatedtherebetween. In one embodiment, the clamp arm maybe configured to applyminimum force at its longitudinal center where the displacementamplitude of the end effector is maximum and apply increasing force toeither side of the center to compensate for the decreasing displacementamplitude along the active length on either side of the center. Forexample, the clamp arm may be configured to exert a normal minimum forceat a point at or near the center of the clamp/arm assembly coincidingwith an antinode of the end effector. The force applied by the clamp armincreases towards either end of the clamp arm. In this manner, the clamparm exerts a force distribution profile over the active length of theend effector that is ideally inversely proportional to the velocitydisplacement amplitude of the end effector. Accordingly, the combinationof the end effector velocity and the force exerted by the clamp arm onthe end effector are substantially constant over the active length ofthe end effector.

In yet another embodiment, an ultrasonic instrument comprises an endeffector may comprise one or more movable “folded elements”. The foldedelement may be slideable, foldable, extendable, flappable, and/orrotatable. For example, an extendable folded element may be extended toprovide a distal end that is selectable from an active cutting and/orcoagulating mode, where the horn element is fully extended, to a dullmode where the horn element is fully retracted, or any mode therebetweenwhere the horn element is located in an intermediate position betweenfully extended and fully retracted. A fully retracted folded elementpresents a dull or minimally active distal end that does not affecttissue in contact therewith. A fully extended folded element presents amaximally active distal end to the affect the tissue in contacttherewith. A partially extended folded element presents a partiallyactive distal end to the tissue in contact therewith.

In still another embodiment, an ultrasonic instrument comprises an endeffector coupled to an acoustic waveguide or horn element. The endeffector may comprise one or more “folded elements”. The folded elementmay be formed as a hook at a distal end of the end effector. The foldedelement may be formed at or near a node, an antinode, or therebetween.In one embodiment, the hook may be formed by folding a distal segment ofthe end effector at a displacement node. In this configuration thedistal end is free and remains a node, e.g., the ultrasonic displacementis minimal or approximately zero. The tip of the folded segment,however, remains an antinode where ultrasonic displacement is at amaximum. Tissue located within the hook may be continuously cut and/orcoagulated. The operation of the hook shaped folded element is describedin more detail below.

The various embodiments of the ultrasonic instruments described abovemay be driven by a conventional transducer configured to producevibrations along a longitudinal axis of an ultrasonic transmissionwaveguide at a predetermined frequency. The end effector comprising thefolded elements (folded element) may be coupled to the transducer viathe waveguide or in direct contact in any suitable manner. The endeffector may comprise a folded element and may be coupled to or form aportion of a waveguide extending along the longitudinal axis coupled tothe transducer. The end effector includes a body comprising a foldedelement having a proximal end and a distal end. The folded element ismovable along the longitudinal axis by the vibrations produced by thetransducer.

FIG. 1 illustrates one embodiment of an ultrasonic system 10 comprisinga single-element end effector. One embodiment of the ultrasonic system10 comprises an ultrasonic signal generator 12 coupled to an ultrasonictransducer 14, a hand piece assembly 60 comprising a hand piece housing16, and an ultrasonically actuatable single-element end effector 50shown as an ultrasonically actuatable blade comprising a folded element53. The ultrasonic transducer 14, which is known as a “Langevin stack”,generally includes a transduction portion 18, a first resonator portionor end-bell 20, and a second resonator portion or fore-bell 22, andancillary components. The total construction of these components is aresonator. The ultrasonic transducer 14 is preferably an integral numberof one-half system wavelengths (nλ/2; where “n” is any positive integer;e.g., n=1, 2, 3 . . . ) in length as will be described in more detailherein. An acoustic assembly 24 includes the ultrasonic transducer 14, anose cone 26, a velocity transformer 28, and a surface 30.

It will be appreciated that the terms “proximal” and “distal” are usedherein with reference to a clinician gripping the hand piece assembly60. Thus, the end effector is distal with respect to the more proximalhand piece assembly 60. It will be further appreciated that, forconvenience and clarity, spatial terms such as “top” and “bottom” alsoare used herein with respect to the clinician gripping the hand pieceassembly 60. However, surgical instruments are used in many orientationsand positions, and these terms are not intended to be limiting andabsolute.

The distal end of the end-bell 20 is connected to the proximal end ofthe transduction portion 18, and the proximal end of the fore-bell 22 isconnected to the distal end of the transduction portion 18. Thefore-bell 22 and the end-bell 20 have a physical length determined by anumber of variables, including the thickness of the transduction portion18, the density and modulus of elasticity of the material used tomanufacture the end-bell 20 and the fore-bell 22, and the resonantfrequency of the ultrasonic transducer 14. The fore-bell 22 may betapered inwardly from its proximal end to its distal end to amplify theultrasonic vibration amplitude as the velocity transformer 28, oralternately may have no amplification. A suitable vibrational frequencyrange may be about 20 Hz to 120 kHz and a well-suited vibrationalfrequency range may be about 30-100 kHz. A suitable operationalvibrational frequency may be approximately 55.5 kHz, for example. Thesecond resonator portion or the fore-bell 22 may be folded to reduce theoverall physical length of the fore-bell 22 while maintaining orincreasing the acoustic length.

Piezoelectric elements 32 may be fabricated from any suitable material,such as, for example, lead zirconate-titanate, lead meta-niobate, leadtitanate, barium titanate, or other piezoelectric ceramic material. Eachof positive electrodes 34, negative electrodes 36, and the piezoelectricelements 32 has a bore extending through the center. The positive andnegative electrodes 34 and 36 are electrically coupled to wires 38 and40, respectively. The wires 38 and 40 are encased within a cable 42 andelectrically connectable to the ultrasonic signal generator 12 of theultrasonic system 10.

The ultrasonic transducer 14 of the acoustic assembly 24 converts theelectrical signal from the ultrasonic signal generator 12 intomechanical energy that results in primarily a standing acoustic wave oflongitudinal vibratory motion of the ultrasonic transducer 14 and theend effector 50 at ultrasonic frequencies. In another embodiment, thevibratory motion of the ultrasonic transducer may act in a differentdirection. For example, the vibratory motion may comprise a locallongitudinal component of a more complicated motion of the tip of theultrasonic system 10. A suitable generator is available as model numberGEN04, from Ethicon Endo-Surgery, Inc., Cincinnati, Ohio. When theacoustic assembly 24 is energized, a vibratory motion standing wave isgenerated through the acoustic assembly 24. The ultrasonic system 10 isdesigned to operate at a resonance such that an acoustic standing wavepattern of predetermined amplitude is produced. The amplitude of thevibratory motion at any point along the acoustic assembly 24 dependsupon the location along the acoustic assembly 24 at which the vibratorymotion is measured. A zero crossing in the vibratory motion standingwave is generally referred to as a node (i.e., where motion is zero),and a local absolute value maximum or peak in the standing wave isgenerally referred to as an antinode (i.e., where local motion ismaximal). The distance between an antinode and its nearest node is onequarter wavelength (λ/4).

The wires 38 and 40 transmit an electrical signal from the ultrasonicsignal generator 12 to the positive electrodes 34 and the negativeelectrodes 36. The piezoelectric elements 32 are energized by theelectrical signal supplied from the ultrasonic signal generator 12 inresponse to an actuator 44, such as a foot switch, for example, toproduce an acoustic standing wave in the acoustic assembly 24. Thealternating electrical signal causes the piezoelectric elements 32 toexpand and contract in a continuous manner along the axis of the voltagegradient, producing longitudinal waves of ultrasonic energy. Theexpansion and contraction produce small displacements alternating indirection resulting in large alternating compression and tension forceswithin the material. An ultrasonic transmission assembly 102 includesthe single-element end effector 50 coupled to an ultrasonic transmissionwaveguide 104. The ultrasonic energy is transmitted through the acousticassembly 24 to the end effector 50 via a transmission component such asthe ultrasonic transmission waveguide 104. The ultrasonic transmissionwaveguide 104 may be preferably fabricated from a hollow core shaftconstructed out of material that propagates ultrasonic energyefficiently, such as titanium alloy (i.e., Ti6Al4V) or an aluminumalloy, for example. In other embodiments, the ultrasonic transmissionwaveguide 104 may be formed as a solid core transmission waveguide.

In order for the acoustic assembly 24 to deliver energy to thesingle-element end effector 50, all components of the acoustic assembly24 are acoustically coupled to the end effector 50. The distal end ofthe ultrasonic transducer 14 may be acoustically coupled at the surface30 to the proximal end of the ultrasonic transmission waveguide 104 by athreaded connection such as a stud 48.

The components of the acoustic assembly 24 are preferably acousticallytuned such that the length of any assembly is an integral number ofone-half wavelengths (nλ/2), where the wavelength λ is the wavelength ofa pre-selected or operating longitudinal vibration drive frequency f_(d)of the acoustic assembly 24. It is also contemplated that the acousticassembly 24 may incorporate any suitable arrangement of acousticelements.

The end effector 50 may have a length substantially equal to an integralmultiple of one-half system wavelengths (nλ/2). The blade comprises adistal end 52, which coincides with the physical distal end of thefolded element 53. The folded element 53 comprises an acoustic distalend 55 located at an antinode in terms of displacement. The acousticdistal end 55 is located at a point of maximum amplitude of thelongitudinal ultrasonic vibration and the ultrasonic displacement is ata maximum. In one embodiment, the distal end 52 of the end effector 50coincides with the distal end of the folded element 53 and may bedisposed near an antinode to provide the maximum longitudinal excursionof the distal end 52. The corresponding proximal end 55 of the foldedelement 53 may be disposed near a node. In another embodiment, thedistal end 52 of the end effector 50 coincides with the distal end ofthe folded element 53 and may be disposed near a node to provide theminimum longitudinal excursion of the distal end 52. The correspondingproximal end 55 of the folded element 53 may be disposed near anantinode to provide the maximum longitudinal excursion of the proximalend 55 of the folded element 53. In other embodiments, the distal end 52of the end effector 50 coincides with the distal end of the foldedelement 53 and may be disposed between a node and an antinode to phasethe longitudinal excursion of the distal end 52 accordingly. In theillustrated embodiment, the distal end 52 of the blade 50 coincides withthe distal end of the folded element 53 and is disposed near a node toprovide the minimum longitudinal excursion of the distal end 52. Thecorresponding proximal end 55 of the folded element 53 is disposed nearan antinode to provide the maximum longitudinal excursion of theproximal end 55 of the folded element 53. When the transducer assemblyis energized, the proximal end 55 of the folded element 53 may beconfigured to move in the range of, for example, approximately 10 to 500microns peak-to-peak, and preferably in the range of about 30 to 150microns at a predetermined vibrational frequency of 55 kHz, for example.

The end effector 50 may be coupled to the ultrasonic transmissionwaveguide 104. The blade 50 and the ultrasonic transmission waveguide104 as illustrated are formed as a single unit construction from amaterial suitable for transmission of ultrasonic energy. Examples ofsuch materials include Ti6Al4V (an alloy of Titanium including Aluminumand Vanadium), Aluminum, Stainless Steel, or other suitable materials.Alternately, the end effector 50 may be separable (and of differingcomposition) from the ultrasonic transmission waveguide 104, and coupledby, for example, a stud, weld, glue, quick connect, or other suitableknown methods. The length of the ultrasonic transmission waveguide 104may be substantially equal to an integral number of one-half wavelengths(nλ/2), for example. The ultrasonic transmission waveguide 104 may bepreferably fabricated from a solid core shaft constructed out ofmaterial suitable to propagate ultrasonic energy efficiently, such asthe titanium alloy discussed above (i.e., Ti6Al4V) or any suitablealuminum alloy, or other alloys, for example.

The ultrasonic transmission waveguide 104 comprises a longitudinallyprojecting attachment post 54 at a proximal end to couple to the surface30 of the ultrasonic transmission waveguide 104 by a threaded connectionsuch as the stud 48. In the embodiment illustrated in FIG. 1, theultrasonic transmission waveguide 104 includes a plurality ofstabilizing silicone rings or compliant supports 56 positioned at aplurality of nodes. The silicone rings 56 dampen undesirable vibrationand isolate the ultrasonic energy from an outer sheath 58 ensuring theflow of ultrasonic energy in a longitudinal direction to the distal end52 of the end effector 50 with maximum efficiency.

As shown in FIG. 1, the outer sheath 58 protects a user of theultrasonic surgical instrument 10 and a patient from the ultrasonicvibrations of the ultrasonic transmission waveguide 104. The sheath 58generally includes a hub 62 and an elongated tubular member 64. Thetubular member 64 is attached to the hub 62 and has an opening extendinglongitudinally therethrough. The sheath 58 is threaded onto the distalend of the velocity transformer 28. The ultrasonic transmissionwaveguide 104 extends through the opening of the tubular member 64 andthe silicone rings 56 isolate the ultrasonic transmission waveguide 104from the outer sheath 58. The outer sheath 58 may be attached to thewaveguide 104 with an isolator pin 114. The hole 116 in the waveguide104 may occur nominally at a displacement node. The waveguide 104 mayscrew or snap onto the hand piece assembly 60 by the stud 48. The flatportions on the hub 62 may allow the assembly to be torqued to arequired level.

The hub 62 of the sheath 58 is preferably constructed from plastic andthe tubular member 64 is fabricated from stainless steel. Alternatively,the ultrasonic transmission waveguide 104 may incorporate a polymericmaterial surrounding it to isolate it from outside contact.

The distal end of the ultrasonic transmission waveguide 104 may becoupled to the proximal end of the single-element end effector 50 by aninternal threaded connection, preferably at or near an antinode. It iscontemplated that the end effector 50 may be attached to the ultrasonictransmission waveguide 104 by any suitable means, such as a welded jointor the like. Although the end effector 50 may be detachable from theultrasonic transmission waveguide 104, it is also contemplated that theend effector 50 and the ultrasonic transmission waveguide 104 may beformed as a single unitary piece. In the illustrated embodiment, theultrasonic waveguide 104 is implemented as an elongated transmissioncomponent and the end effector is implemented as a single-element endeffector or the end effector 50 suitable to cut and/or coagulate tissue.The end effector 50 may be symmetrical or asymmetrical.

FIG. 2A illustrates one embodiment of an ultrasonic system 1000comprising a multi-element end effector. One embodiment of theultrasonic system 1000 comprises the ultrasonic generator 12 coupled tothe ultrasonic transducer 14 previously described with reference toFIG. 1. The ultrasonic transducer 14 is coupled to clamping coagulatingshears 1002 comprising an instrument housing 1004. The acoustic assembly18 delivers energy to a multi-element end assembly 1008 comprising anultrasonic end effector 1016 shown in the form of an ultrasonicallyactuable blade. In order for the acoustic assembly 18 to deliver energyto the end effector 1016 portion of the multi-element end assembly 1008,all components of the acoustic assembly 18 are acoustically coupled tothe ultrasonically active portions of the clamping coagulating shears1002. Accordingly, the distal end of the ultrasonic transducer 14 may beacoustically coupled via the surface 30 to the proximal end of theultrasonic transmission waveguide 104 by way of the threaded connectionstud 48.

As previously discussed with reference to the ultrasonic system 10 shownin FIG. 1, the components of the acoustic assembly 18 are preferablyacoustically tuned such that the length of any assembly is an integralnumber of one-half wavelengths (nλ/2), where the wavelength λ is thewavelength of a pre-selected or operating longitudinal vibration drivefrequency f_(d) of the acoustic assembly 18. The acoustic assembly 18may incorporate any suitable arrangement of acoustic elements.

The clamping coagulating shears 1002 may be preferably attached to andremoved from the acoustic assembly 18 as a unit. The proximal end of theclamping coagulating shears 1002 preferably acoustically couples to thedistal surface 30 of the acoustic assembly 18. The clamping coagulatingshears 1002 may be coupled to the acoustic assembly 18 by any suitablemeans.

The clamping coagulating shears 1002 preferably includes an instrumenthousing 1004 and an elongated member 1006. The elongated member 1006 maybe selectively rotated with respect to the instrument housing 1004 viathe rotation knob 1010. The instrument housing 1004 includes a pivotinghandle portion 1028 and a fixed handle portion 1029.

An indexing mechanism (not shown) is disposed within a cavity of theinstrument housing 1004 and is preferably coupled or attached on aninner tube 1014 to translate movement of the pivoting handle portion1028 to linear motion of the inner tube 1014 to open and close themulti-element end assembly 1008. The pivoting handle portion 1028includes a thumb loop 1030. A pivot pin is disposed through a first holeof the pivoting handle portion 1028 to allow pivoting. As the thumb loop1030 of the pivoting handle portion 1028 is moved in the direction ofarrow 1034, away from the instrument housing 1004, the inner tube 1014slides distally away from the proximal end to pivot the clamp arm 1018of the multi-element end assembly 1008 into an open position in thedirection indicated by arrow 1020. When the thumb loop 1030 of thepivoting handle portion 1028 is moved in the opposite direction towardthe fixed handle portion 1029 in the direction indicated by arrow 1035,the indexing mechanism slides the inner tube 1014 proximally away fromthe distal end to pivot the clamp arm 1018 of the multi-element endassembly 1008 into a closed position, as shown.

The elongated member 1006 of the clamping coagulating shears 1002extends from the instrument housing 1004. The elongated member 1006preferably includes an outer member or outer tube 1012, an inner memberor inner tube 1014, and a transmission component or ultrasonictransmission waveguide 104.

The multi-element end assembly 1008 includes a clamp arm 1018 (or clamparm assembly) and the ultrasonic end effector 1016. The ultrasonic endeffector 1016 comprises folded elements as described in more detailbelow in FIGS. 4-21. The ultrasonic blade 1016 may be symmetrical orasymmetrical. In one embodiment, the clamp arm 1018 may comprise atissue pad. Accordingly, the clamp arm 1018 may be referred to as aclamp arm assembly, for example. The clamp arm 1018 may be configured toapply a compressive or biasing force to the tissue to achieve fastercoagulation and cutting of the tissue. The clamp arm 1018 is pivotallymounted about a pivot pin (not shown) to rotate in the directionindicated by arrow 1020. The clamp arm 1018 may be configured to createa predetermined force distribution profile along the length (preferablyalong the active length) of the clamp arm 1018. In the illustratedembodiment, the clamp arm 1018 applies the predetermined force profilesubstantially over the entire active length of the end effector 1016. Ata center region, the clamp arm 1018 may exert a minimum force at a pointcoinciding with an antinode of the end effector 1016. A normal force isapplied to the end effector 1016 by a reciprocating outer compressiontube 1019 at or near the center of the clamp arm 1018. From the centerof the clamp arm 1018, (e.g., the point of minimum force exerted by theclamp arm 1018) the force exerted by the clamp arm 1018 increases fromthe center outwardly towards the proximal end and the distal end toeither side of the center of the clamp arm 1018 towards the ends of theclamp arm 1018. In this manner, the clamp arm 1018 exerts a forcedistribution profile over the active length of the end effector 1016that is ideally inversely proportional to the velocity amplitudedisplacement of the end effector 1016. The combination of the velocityof the end effector 1016 and the force exerted by the clamp arm 1018determines the force profile along the active length of the end effector1016.

Components of the ultrasonic surgical systems 10 and 1000 may besterilized by methods known in the art such as, for example, gammaradiation sterilization, Ethylene Oxide processes, autoclaving, soakingin sterilization liquid, or other known processes. In the embodimentillustrated in FIG. 1, the end effector 50 and the ultrasonictransmission waveguide 104 are illustrated as a single unit constructionfrom a material suitable for transmission of ultrasonic energy aspreviously discussed (e.g., Ti6Al4V, Aluminum, Stainless Steel, or otherknown materials). Alternately, the end effector 50 may be separable (andof differing composition) from the ultrasonic transmission waveguide104, and coupled by, for example, a stud, weld, glue, quick connectmechanism, or other known methods. In the embodiment illustrated in FIG.2, the ultrasonic transmission assembly 1024 of the clamping coagulatingshears 1002 includes the multi-element end assembly 1008 coupled to theultrasonic transmission waveguide 104. The length of the ultrasonictransmission waveguide 104 may be substantially equal to an integralnumber of one-half system wavelengths (nλ/2), for example.

FIG. 2B illustrates one embodiment of the multi-element end assembly1008. As illustrated, the multi-element end assembly 1008 comprises anarcuate clamp arm 1018 (or clamp arm assembly) and the ultrasonic andeffector 1016. The ultrasonic end effector 1016 comprises foldedelements as described in more detail below. The ultrasonic end effector1016 may be symmetrical or asymmetrical. In one embodiment, a clamp armassembly comprises the clamp arm 1018 with a tissue pad 1021. The clamparm 1018 may be configured to apply a compressive or biasing force totissue 1025 (FIGS. 2C, 2D) located between the tissue pad 1021 and theultrasonic end effector 1016 to achieve faster coagulation and cuttingof the tissue 1025. The compressive force may be applied by sliding thereciprocating outer compression tube 1019 over the clamp arm 1018. Theclamp arm 1018 is pivotally mounted about a pivot 1023 to rotate open inthe direction indicated by arrow 1020 and rotate closed in the directionindicated by arrow 1027. The clamp arm 1018 is configured to create apredetermined force distribution profile along the length of the clamparm 1018 and the active length of the ultrasonic end effector 1016.

FIGS. 2C and 2D illustrate the clamp arm in various stages. FIG. 2Cillustrates the clamp arm 1018 in an open position ready to receive thetissue 1025 between the tissue pad 1021 and the end effector 1016. Thereciprocating outer compression tube 1019 is in a retracted position toenable the clamp arm 1018 to rotate in direction 1020 about the pivot1023 to an open position. FIG. 2D illustrates the clamp arm 1018 rotatedabout the pivot 1023 to rotate in direction 1027 to a closed positionwith the reciprocating outer compression tube 1019 partially slid indirection 1029 over the clamp arm 1018 applying a partial compressiveforce over the clamp arm 1018. As illustrated in FIG. 2A, thereciprocating outer compression tube 1019 is located in a fully extendedposition to apply a full compressive force against the clamp arm 1018.Accordingly, the clamp arm 1018 applies a predetermined forcedistribution profile along the length of the clamp arm 1018 and theactive length of the end effector 1016.

FIG. 3 illustrates one embodiment of a connection union/joint 70 for anultrasonic instrument. The connection union/joint 70 is located betweenthe acoustic assembly 24 and an ultrasonic transmission component suchas the ultrasonic transmission waveguide 104, for example. Theconnection union/joint 70 may be formed between an attachment post 54 ofthe ultrasonic transmission waveguide 104 and the surface 30 of thevelocity transformer 28 located at the distal end of the acousticassembly 24. The proximal end of the attachment post 54 comprises afemale threaded substantially cylindrical recess 66 to receive a portionof the threaded stud 48 therein. The distal end of the velocitytransformer 28 also may comprise a female threaded substantiallycylindrical recess 68 to receive a portion of the threaded stud 48. Therecesses 66 and 68 are substantially circumferentially andlongitudinally aligned. In another embodiment (not shown), the stud maybe formed as an integral component of the end of the ultrasonictransducer 14 shown in FIG. 1. For example, the threaded stud and thevelocity transformer may be formed as a single unit construction withthe stud projecting from a distal surface of the velocity transformer atthe distal end of the acoustic assembly. In this embodiment, the stud isnot a separate component and does not require a recess in the end of thetransducer.

Those of ordinary skill in the art will understand that the variousembodiments of the ultrasonic surgical instruments disclosed herein aswell as any equivalent structures thereof could conceivably beeffectively used in connection with other known ultrasonic surgicalinstruments without departing from the scope thereof. Thus, theprotection afforded to the various ultrasonic surgical end effectorembodiments disclosed herein should not be limited to use only inconnection with the exemplary ultrasonic surgical instrument describedabove.

In the ensuing description, the letter “A” denotes the location of adisplacement antinode and the letter “N” denotes the location of adisplacement node. The distance between an antinode “A” and its nearestnode “N” is one quarter wavelength (λ/4). One quarter wavelength (λ/4)is primarily determined by the frequency and speed of sound in thematerial. The speed of sound in most metals suitable for ultrasoniccomponents is nominally 5,000 meters per second. Unless otherwisestated, in the embodiments described herein the wavelength is determinedat an excitation frequency of 55.5 kHz where the wavelength isapproximately 3.58 inches and one quarter wavelength (λ/4) isapproximately 0.886 inches. For a waveguide formed of Ti6Al4V with awave speed of 16,011 feet per second (4880 meters per second) thequarter wavelength is approximately 0.866 inches. Other materials thatmay lead to longer or shorter wavelengths may be employed. The activelength in Ti6Al4V is nominally approximately 0.6 inches (≈15 mm).

FIG. 4 is a schematic diagram of one embodiment of a hollow tubular endeffector 400. FIG. 4A is a longitudinal cross-sectional view of the endeffector 400. FIG. 4B is a cross-sectional view of the end effector 400taken along line 4B-4B. A characteristic ultrasonic displacement curve420 for the end effector 400 is graphically illustrated in FIG. 7 and isdescribed in more detail below. With reference to FIGS. 4, 4A, and 4B,the end effector 400 comprises a body 406 having a proximal end 402, adistal end 404, and a cylindrical outer surface. The end effector 400 isdescribed as a reference to facilitate understanding of the operation ofthe end effectors with folded elements in the embodiments shown in FIGS.5 and 6. In the embodiment illustrated in FIG. 4, the end effector 400has a physical length “L” of three quarter wavelengths (3λ/4). The endeffector 400 may be formed of Ti6Al4V excited at a frequency of 55.5kHz. Thus, one quarter wavelength (λ/4) is approximately 0.866 inches.Other materials that may provide longer or shorter wavelengths may beemployed. The active length in Ti6Al4V is nominally approximately 0.6inches (≈15 mm).

In the illustrated embodiments, the proximal end 402 of the end effector400 is located at the left side and the distal end 404 of the endeffector 400 is located at the right side of the end effector 400. Fromleft to right, the first quarter wavelength extends between the firstnode N1 and the first antinode A1; the second quarter wavelength extendsbetween the first antinode A1 and the second node N2; and the thirdquarter wavelength extends between the second node N2 and the secondantinode A2. The first node N1 is located at the proximal end 402 andthe second antinode A2 is located at the distal end 404. It will beappreciated that in other embodiments, the end effector 400 may have aphysical length that is an integer multiple of one quarter wavelength(nλ/4; where “n” is any positive integer; e.g., n=1, 2, 3 . . . ). Theproximal end 402 of the end effector 400 is configured to couple to thevelocity transformer 28 at the surface 30 as shown in FIGS. 1 and 2A.The proximal end 402 may be connected to or be a part of an additionaltransmission waveguide extending further in the proximal direction. Fordirect connection to the velocity transformer 28, the end effector 400may be extended proximally by one quarter wavelength (λ/4) so that theproximal end 402 coincides with an antinode. Accordingly, the velocitytransformer 28 and the end effector 400 may be joined together at theirrespective antinodes and the system frequency remains near the desirednominal value. In one embodiment, the nominal frequency is 55.5 kHz, forexample. The added proximal quarter wavelength may have the same area asthe outside parallel path (i.e., extended proximally by a quarter wavelength). In which case, there is no gain. If the proximal segment has anincreased area, then there will be amplitude gain due to the decrease inarea relative to end effector 400 this represents. The end effector 400may include gain, attenuation, and other features to achieve a desiredperformance as an ultrasonic surgical instrument operating at 55.5 kHz,for example. As shown in FIG. 4, the distal end 404 coincides with thesecond antinode A2 and, therefore, the distal end 404 is a point ofmaximum amplitude of the longitudinal ultrasonic vibration and theultrasonic displacement is at a maximum. Conversely, the proximal end402 coincides with the first node N1 and, therefore, the proximal end402 is a point of minimum amplitude of the longitudinal ultrasonicvibration and the ultrasonic displacement is at a minimum.

FIG. 5 is a schematic diagram of one embodiment of an end effector 408comprising a folded element 418 defining a parallel acoustic path. FIG.5A is a longitudinal cross-sectional view of the end effector 408. FIG.5B is a cross-sectional view of the end effector 408 taken along line5B-5B. In one embodiment, the end effector 408 is suitable for use inthe embodiment of the single-element end effector ultrasonic system 10shown in FIG. 1. In another embodiment, the end effector 408 may besuitably adapted for use in the embodiment of the multi-element endeffector system 1000 shown in FIG. 2A. A characteristic ultrasonicdisplacement curve 430 for the end effector 408 is graphicallyillustrated in FIG. 8 and is described in more detail below. The endeffector 408 will now be described with reference to FIGS. 5, 5A, and5B. The end effector 408 is a hollow tube ultrasonic transmission linecomprising a body 410 having a proximal end 414 and a distal end 416with a folded element 412 coupled to (e.g., folded at) the distal end416 at the second node N2. The folded element 412 extends proximallyfrom the second node N2 located at the distal end 416 towards theproximal end 414 into a hollow portion 413 of the end effector 408 tothe first antinode A1. An acoustic distal end 418 of the folded element412 terminates at the first antinode A1, where the first antinode A1coincides with the second antinode A2. The first and second antinodesA1, A2 coincide when an end effector is folded at a node N and thelength of the folded element is one quarter wavelength (λ/4). If thelength of the folded element 412 is greater than or less than onequarter wavelength (λ/4), the first and second antinodes A1, A2 will notcoincide. For example, if the fold is made between a node (N) and anantinode (A), the first and second antinodes A1, A2 will not coincideeven if the length of the folded element 412 is one quarter wavelength(λ/4). These configurations are described herein below. In theillustrated embodiment, reference to the second antinode A2 is mademerely to facilitate understanding the relation between the location ofthe fold and the length of the folded element 412. In the illustratedembodiment, the folded element 412 extends parallel to the longitudinalaxis and to an outer surface of the body 410 of the end effector 408.The folded element 412 and the outer body of 410 of the end effector 408define a parallel acoustic path 417 spanning the length of the foldedelement 412. In the illustrated embodiment, the parallel acoustic path417 extends between the first antinode A1 and the second node N2. Theend effector 408 in the illustrated embodiment has a physical length“L1” of two quarter wavelengths (L1=2λ/4). The folded element 412 is asolid rod. Over its length, the cross-sectional area of the foldedelement 412 is substantially equal to the longitudinal cross-sectionalarea of the end effector 408. The folded element 412 forms the distalquarter wavelength (λ/4) of the end effector 408. It will be appreciatedthat the physical length of the end effector 408 may be an integermultiple of one quarter wavelength (nλ/4; where “n” is any positiveinteger; e.g., n=1, 2, 3 . . . ). Similarly, the folded element 412 mayhave a physical length that is an integer multiple of one quarterwavelength (nλ/4; where “n” is any positive integer; e.g., n=1, 2, 3 . .. ). The embodiments are not limited in this context.

The proximal end 414 of the end effector 408 may be configured to coupleto the velocity transformer 28 at the surface 30 as shown in FIGS. 1 and2A. The proximal end 414 may be connected to or may form a portion of anultrasonic transmission waveguide extending further in the proximaldirection. For direct connection to the velocity transformer 28, the endeffector 408 may be extended proximally by one quarter wavelength (λ/4)so that the proximal end 414 coincides with an antinode. Accordingly,the velocity transformer 28 and the end effector 408 may be joinedtogether at their respective antinodes and the system frequency remainsnear the desired nominal value. In one embodiment, the nominal frequencyis 55.5 kHz, for example. The added proximal quarter wavelength may havethe same area as the outside parallel path (i.e., extended proximally bya quarter wave length). In which case, there is no gain. If the proximalsegment has an increased area, then there will be amplitude gain due tothe decrease in area with respect to 410 this represents. The endeffector 408 may include gain, attenuation, and other features toachieve a desired performance as an ultrasonic surgical instrumentoperating at 55.5 kHz, for example. The end effector 408 comprises afree distal end 416 that coincides with the second node N2. The distalend 416 is a region of minimum amplitude displacement. The acousticdistal end 418 is located at a proximal end of the folded element 412.In the illustrated embodiment, the acoustic distal end 418 coincideswith the first and second antinodes A1, A2 in terms of displacement. Theacoustic distal end 418 is a region of maximum amplitude displacement.The external portion of the end effector 408 has a maximum displacementat its center located at the first antinode A1. Because the amplitudefalls off symmetrically on either side of the first antinode A1, theactive length is approximately 1.2 inches (≈30 mm). This is double theactive length of approximately 0.6 inches (≈15 mm) of the end effector400 illustrated in FIG. 4. In the end effector 400 the active length ismeasured from the second antinode A2 at the distal end 404 where themaximum amplitude displacement occurs to a point where the amplitudedrops of to 50% of maximum somewhere between the second antinode A2 andthe second node N2.

In other embodiments, the physical length of the folded element 412 maybe greater than or less than one quarter wavelength (λ/4), or may beless than an integer multiple thereof (nλ/4), such that the ultrasonicamplitude displacement of the acoustic distal end 418 of the endeffector 408 can be phased between maximum displacement and minimumdisplacement by suitably selecting the length of the folded element 412.In such embodiments, the length of the end effector 408 may be greaterthan or less than any number of quarter wavelengths (λ/4). It will beappreciated by those skilled in the art that in the various embodimentsdescribed herein, the length L1 of the end effector 408 is longer thanthe length of the folded segment 412. Nevertheless, the combined lengthof the end effector 408 and the folded element 412 may be any suitablenumber of quarter wavelengths (λ/4). In one embodiment, a particularlybeneficial position for locating the fold is at in the region betweenthe first antinode A1 and the second node N2 where the displacementamplitude drops off to 50% of maximum. Accordingly, the distal end 416occurs at the limit of the active length. Moving towards the proximalend 414, the displacement amplitude remains above the minimum effectiveamplitude (>50% of maximum) to a region beyond the first antinode A1.Moving further towards the proximal end 414, the amplitude begins todrop below the desired 50% amplitude level. In this manner, the activelength for end effectors designed with titanium (Ti) operating at 55.5kHz may be extended to approximately 1.2 inches (≈30 mm).

At the location of the “fold”, the longitudinal extension of the endeffector 408 retains the ultrasonic displacement characteristics of thatlocation without the fold. For example, in the embodiments illustratedin FIGS. 5, 5A, and 5B, the fold is located at the second node N2, atthe distal end 416, and the folded element 412 extends proximally onequarter wavelength (λ/4) from the distal end 416 to the first and secondantinodes A1, A2, which coincide with the acoustic distal end 418. Thedisplacement pattern and locations of the first and second nodes N1, N2remain the same along the longitudinal length of the end effector 408.The second node N2 remains a node, e.g., minimum or no displacementamplitude, even though it “presents” a free-end. Accordingly, the distalend 416 of the end effector 408 has substantially zero displacement andremains dull even when it is ultrasonically activated. This feature maybe desirable in certain procedures to protect tissue that may come intocontact with or may be in proximity to the distal end 416. Otherwise, anactive distal end may create a surgical window or -otomy through thetissue it comes into contact with. Those skilled in the art willappreciate that the term “-otomy” refers to a combining form meaning“cutting, incision” of tissue or an organ, “excision” of an object, asspecified by the initial element.

FIG. 6 is a schematic diagram of one embodiment of an end effector 438comprising a folded element 442 defining a parallel acoustic path. FIG.6A is a longitudinal cross-sectional view of the end effector 438. FIG.6B is a cross-sectional view of the end effector 438 taken along line6B-6B. In one embodiment, the end effector 438 is suitable for use inthe embodiment of the single-element end effector ultrasonic system 10shown in FIG. 1. In another embodiment, the end effector 438 may besuitably adapted for use in the embodiment of the multi-element endeffector system 1000 shown in FIG. 2A. The end effector 438 will now bedescribed with reference to FIGS. 6, 6A, and 6B. The end effector 438 isa substantially solid ultrasonic transmission line comprising a body 440having a proximal end 444 and a distal end 446 and the folded element442 coupled to the distal end 446 at the second node N2. The endeffector 438 comprises a slot 445 formed in a distal end of the solidportion 443 thereof. The folded element 442 extends proximally from thesecond node N2 located at the distal end 446 into the slot 445 parallelto the longitudinal axis towards the proximal end 444 to the firstantinode A1. An acoustic distal end 448 of the folded element 442terminates at the first antinode A1, where the first antinode A1coincides with the second antinode A2. The first and second antinodesA1, A2 coincide when an end effector is folded at a node N and thelength of the folded element is one quarter wavelength (λ/4). If thelength of the folded element 442 is greater than or less than onequarter wavelength (λ/4), the first and second antinodes A1, A2 will notcoincide. Also, if the fold is made between a node (N) and an antinode(A), the first and second antinodes A1, A2 will not coincide even if thelength of the folded element 442 is one quarter wavelength (λ/4). Theseconfigurations are described herein below. In the illustratedembodiment, reference to the second antinode A2 is made merely tofacilitate understanding the relationship between the location of thefold and the length of the folded element 442. In the illustratedembodiment, the folded element 442 extends parallel to the longitudinalaxis and to an outer surface of the body 440 of the end effector 408.The folded element 442 and an external surface of the body 440 of theend effector 438 define a parallel acoustic path 447 spanning the lengthof the folded element 442. In the illustrated embodiment, parallelacoustic path 447 extends between the first antinode A1 and the secondnode N2. In the illustrated embodiment, the folded element 442 isconfigured as a rod of rectangular cross section extending in the slot445 formed within the end effector 438. In the illustrated embodiment,the end effector 438 has a physical length “L1” of two quarterwavelengths (2λ/4). The folded element 442 may have a physical length ofapproximately one quarter wavelength (λ/4). Over its length, thelongitudinal cross-sectional area of the folded element 442 issubstantially equal to the longitudinal cross-sectional area of the endeffector 438. It will be appreciated that the physical length of thefolded transmission end effector 438 may be an integer multiple of onequarter wavelength (nλ/4; where “n” is any positive integer; e.g., n=1,2, 3 . . . ). Similarly, the folded element 442 may have a physicallength that is an integer multiple of one quarter wavelength (nλ/4;where “n” is any positive integer; e.g., n=1, 2, 3 . . . ). Theembodiments are not limited in this context.

The proximal end 444 of the end effector 438 is configured to couple tothe velocity transformer 28 at the surface 30 as shown in FIGS. 1 and2A. The proximal end 444 may be connected to or may form a portion of anadditional transmission waveguide extending further in the proximaldirection. For direct connection to the velocity transformer 28, the endeffector 438 may be extended proximally by one quarter wavelength (λ/4)so that the proximal end 444 coincides with an antinode. Accordingly,the velocity transformer 28 and the end effector 438 may be joinedtogether at their respective antinodes and the system frequency remainsnear the desired nominal value. In one embodiment, the nominal frequencyis 55.5 kHz, for example. The added proximal quarter wavelength may havethe same area as the outside parallel path (i.e., extended proximally bya quarter wave length). In which case, there is no gain. If the proximalsegment has an increased area, then there will be amplitude gain due tothe decrease in area with respect to 438 this represents. The endeffector 438 may include gain, attenuation, and other features toachieve a desired performance as an ultrasonic surgical instrumentoperating at 55.5 kHz, for example. The end effector 438 comprises afree distal end 446 that coincides with the second node N2. The distalend 446 is a region of minimum amplitude displacement. The acousticdistal end 448 is located at a proximal end of the folded element 442.In the illustrated embodiment, the acoustic distal end 448 coincideswith the first and second antinodes A1, A2 in terms of displacement. Theacoustic distal end 448 is a region of maximum amplitude displacement.The external portion of the end effector 438 has a maximum displacementat its center located at the first antinode A1. Because the amplitudefalls off symmetrically on either side of the first antinode A1, theactive length is approximately 1.2 inches (≈130 mm). This is double theactive length of approximately 0.6 inches (≈15 mm) of the end effector400 illustrated in FIG. 4.

In other embodiments, the physical length of the folded element 442 maybe greater than or less than one quarter wavelength (λ/4), or maybe lessthan an integer multiple thereof (nλ/4), such that the ultrasonicdisplacement of the acoustic distal end 448 of the end effector 438 canbe phased between maximum displacement and minimum displacement bysuitably selecting the length of the folded element 442. In suchembodiments, the length of the end effector 438 may be greater than orless than any number of quarter wavelengths (λ/4). It will beappreciated by those skilled in the art that in the various embodimentsdescribed herein, the length L1 of the end effector 438 is longer thanthe length of the folded element 442. Nevertheless, the combined lengthof the end effector 438 and the folded element 442 may be any suitablenumber of quarter wavelengths (λ4). In one embodiment, a particularlybeneficial position for locating the fold is at in the region betweenthe first antinode A1 and the second node N2 where the displacementamplitude drops off to 50% of maximum. Accordingly, the distal end 446occurs at the limit of the active length. Moving towards the proximalend 444, the displacement amplitude remains above the minimum effectiveamplitude (>50% of maximum) to a region beyond the first antinode A1.Moving further towards the proximal end 444, the amplitude begins todrop below the desired 50% amplitude level. In this manner, the activelength for end effectors designed with titanium (Ti) operating at 55.5kHz may be extended to approximately 1.2 inches (≈30 mm).

At the location of the “fold”, the longitudinal extension of the endeffector 438 retains the ultrasonic displacement characteristics of thatlocation without the fold. For example, in the embodiments illustratedin FIGS. 6, 6A, and 6B, the fold is located at the second node N2, atthe distal end 446, and the folded element 442 extends proximally onequarter wavelength (λ/4) from the distal end 446 to the first and secondantinodes A1, A2, which coincide with the acoustic distal end 448. Thedisplacement pattern and locations of the first and second nodes N1, N2remain the same along the longitudinal length of the end effector 438.The second node N2 remains a node, e.g., minimum or no displacementamplitude, N2 even though it “presents” a free-end. Accordingly, thedistal end 446 of the end effector 438 has substantially zerodisplacement and remains dull even when it is ultrasonically active.This feature may be desirable in certain procedures to protect tissuethat may come into contact with or may be in proximity to the distal end446. Otherwise, an active distal end may create a surgical window or-otomy through the tissue it comes into contact with.

FIG. 7 graphically illustrates a characteristic ultrasonic displacementcurve 420 for the end effector 400 shown in FIGS. 4, 4A, and 4B. Thedisplacement curve 420 illustrates displacement in terms of ultrasonicamplitude along the vertical axis and quarter wavelengths (λ/4) alongthe horizontal axis. The ultrasonic amplitude of the displacement curve420 is approximately zero at the proximal end 402, which is the locationof the first node N1. The first antinode A1 is located one quarterwavelength (λ/4) from the proximal end 402. Moving distally along theend effector 400, the ultrasonic amplitude of the displacement curve 420at the first (e.g., proximal) antinode A1 is −1 (−100%), meaning thatthe first antinode A1 is a location of maximum or peak ultrasonicdisplacement. It is noted that the negative sign represents the phase ofthe ultrasonic displacement at the first antinode A1 relative to thesecond (e.g., distal) antinode A2. The displacement, however, may becharacterized as temporal oscillations in accordance with equation (1)above. The second node N2 is located two quarter wavelengths (2λ/4) fromthe proximal end 402. Moving distally along the end effector 400, theultrasonic amplitude of the displacement curve 420 at the second node N2is zero. The second antinode A2 is located at the distal end 404, whichis located at a distance of three quarter wavelengths (3λ/4) from theproximal end 402. Moving distally along the end effector 400, theamplitude of the displacement curve 420 at the second antinode A2 is +1(+100%), meaning that the second antinode A2 is a location of maximum orpeak ultrasonic displacement. As previously discussed, the active lengthof an ultrasonic instrument generally may be defined as the distancefrom an active distal end of an end effector (where ultrasonicdisplacement is at a maximum) to a proximal location along the endeffector where the ultrasonic displacement amplitude drops below apredetermined level, such as 50%, as approaching a node (whereultrasonic displacement is at a minimum) is approached. As shown in FIG.7, the end effector 400 has an active length 422 that extends from thesecond antinode A2 located at the distal end 404 to a proximal location424, where the ultrasonic displacement drops to +0.5 (+50%), or onehalf-peak level. The proximal location 424 is located within the thirdquarter wavelength portion. For the displacement curve 420 shown in FIG.7, the active length 422 is approximately 0.65 quarter wavelengths orapproximately 0.6 inches (≈15 mm).

FIG. 8 graphically illustrates an ultrasonic displacement curve 430 forthe end effectors 408 and 438 shown in FIGS. 5, 5A, 5B, and FIGS. 6, 6A,6B respectively. The displacement curve 430 illustrates displacement interms of ultrasonic amplitude along the vertical axis and quarterwavelengths (λ/4) along the horizontal axis. The ultrasonic amplitude ofthe displacement curve 430 is approximately zero at the proximal end414, which is the location of the first node N1. The first antinode A1is located one quarter wavelength (λ4) from the proximal end 414. Movingdistally along the outer segments 410 and 440 of the end effectors 408,438, the ultrasonic amplitude of the displacement curve 430 at the first(e.g., proximal) antinode A1 is +1 (+100%), meaning that the firstantinode A1 is a location of maximum or peak ultrasonic displacement.The second node N2 is located two quarter wavelengths (2λ/4) from theproximal end 414. Moving distally along the end effector 408, 438, theamplitude of the displacement curve 430 at the second (e.g., distal)node N2 also is approximately zero. As shown in FIG. 8, the end effector408, 438 has an active length 432 defined as the distance from aproximal location 434 a, where the ultrasonic displacement curve 430crosses above an ultrasonic amplitude of +0.5 (+50%), e.g., onehalf-peak level, to a distal location 434 b, where the ultrasonicdisplacement curve 430 crosses below an ultrasonic amplitude of +0.5(+50%), e.g., one half-peak level. For the displacement curve 430 shownin FIG. 8, the active length 432 is approximately 1.3 quarterwavelengths or approximately 1.2 inches (≈30 mm). The peak displacementof the ultrasonic displacement curve 430 occurs in the middle of theactive length 432 at the antinode A1. It decreases to either side of themiddle as the first and second end nodes N1, N2 are approached. By wayof comparison, the active length of the end effector 408, 438 is thusapproximately double that of the end effector 400 shown in FIG. 4.

FIG. 9 illustrates a schematic diagram of one embodiment of amulti-element end effector 450 comprising the folded element 412defining a parallel acoustic path 417. The multi-element end effector450 is suitable for use in the embodiment of the multi-element endeffector ultrasonic system 1000 shown in FIG. 2A. The multi-element endeffector 450 comprises the end effector 408 operatively coupled to aclamp arm 452. The clamp arm 452 may comprise a tissue pad 454.

The ultrasonic amplitude displacement profile of the active lengthregion of the end effector 408 requires a predetermined force profile bythe clamp arm 452. In conventional end effectors, the ultrasonicamplitude displacement decreases moving proximally from the antinode (A)towards the node (N). The active length is defined as the region betweena node (N) and an antinode (A) where the ultrasonic displacement remainsat or above 50% of the maximum ultrasonic displacement within theregion. It has been shown that at least to a first order that thegeneration of heat follows a simple frictional law, which may beexpressed formulaically according to equation (2) as follows:

Heat=μvN  (2)

where:

μ=a coefficient of friction;

v=the root mean squared (rms) value of the ultrasonic velocity; and

N=normal force.

To compensate for decreasing amplitude, and hence decreased ultrasonicvelocity, in region away from the distal end of the end effector,conventional clamp arm assemblies generate the highest pressure at aproximal end of the end effector near the location of a clamp arm pivotpoint. This is generally accomplished by hinging the clamp arm at ornear a distal node (N). As the clamp arm closes, the clamping force isgreatest near the pivot point or juncture formed between the clamp armand the end effector. Such conventional clamping mechanism may beneither optimum nor suitable for the amplitude displacement profilegraphically illustrated in FIG. 8. As shown in FIG. 8, the displacementcurve 430 is maximum in a center region at the first antinode A1 anddecreases symmetrically away from the centrally located antinode A1towards the first and second nodes N1, N2 to either side of the antinodeA1.

The clamp arm 452 may be configured to apply a force against the endeffector 408 that is inversely proportional to the displacement curve430 (FIG. 8) of the end effector 408. The force distribution profileproduced by the clamp pad/arm 452 is the inverse of the amplitude curveso that the product of ultrasonic velocity of the end effector 408 andthe force against it remains nominally constant over the active lengthregion. In both concepts the normal force would be applied at the centerof the clamp arm/pad. Accordingly, in one embodiment, the clamp arm 452may be configured as a leaf-spring like mechanism to apply a normalforce 456 at the first antinode A1 of the end effector 408, a normalforce 457 a at a proximal end of the end effector 408, and a normalforce 457 b at a distal end of the end effector 408. In the illustratedembodiment when the clamp mechanism is fully engaged, the normal force456 applied at the first antinode A1 is less than the normal forces 457a, 457 b applied at the respective proximal and distal ends of the endeffector 408. In one embodiment, the clamp arm 452 may comprise a leafspring mechanism in the form of a slender arc-shaped length of springsteel of rectangular cross-section. Those skilled in the art willappreciate that other clamp pad/arm mechanisms may be employed to createa near symmetric force distribution from a center point that decreasefrom the center and increase towards the ends.

FIG. 10 illustrates a schematic diagram of one embodiment of amulti-element end effector 460 comprising the folded element 412defining a parallel acoustic path. The multi-element end effector 460 issuitable for use in the embodiment of the multi-element end effectorultrasonic system 1000 shown in FIG. 2A. The multi-element end effector460 comprises the end effector 408 operatively coupled to a hinged clamparm assembly 462. The hinged clamp arm assembly 462 comprises first andsecond tissue pad members 464 a, b. The hinged clamp arm assembly 462may comprise a hinge configuration in the form of a first member 462 aand a second member 462 b coupled at a pivot point 468. The first andsecond members 462 a, b are adapted to receive the corresponding firstand second tissue pad members 464 a, b. A spring 470 applies a force tothe hinged first and second clamp arm members 462 a, b. The spring 470may be a torsional spring, flat spring, or any other suitable type ofspring known in the art. The hinge also may be a living hinge wherethere is a central segment that is thinned out relatively to the longersegments of the clamp arm on either side. Those skilled in the art willappreciate that living hinges are well known in the field of mechanicaldesign.

In one embodiment, the hinged clamp arm assembly 462 may be configuredas a hinge-like mechanism comprising a pivot point 468 to apply thegreatest forces 467 a, b at the ends of the active length region of theend effector 408 with sufficient force 466 at the center located at thefirst antinode A1. The forces 466 and 467 a, b applied by the clamp arm462 against the end effector 408 are ideally inversely proportional tothe displacement curve 430 graphically illustrated in FIG. 8.

FIG. 11 illustrates a longitudinal cross-sectional view of oneembodiment of an extendable tubular end effector 478. In one embodiment,the end effector 478 is suitable for use in the embodiment of thesingle-element end effector ultrasonic system 10 shown in FIG. 1. Inanother embodiment, the end effector 478 may be suitably adapted for usein the embodiment of the multi-element end effector system 1000. The endeffector 478 comprises a body 480 having a proximal end 484 and a distalend 486 and a folded element 482 slideably coupled to the body 480. Inthe illustrated embodiment, the end effector 478 is a tubular endeffector shown in the extended configuration. The folded element 482 isslideably moveable in the directions indicated by arrows 490 a, b alongthe longitudinal axis. Once it is extended, the folded element 482 islocked in place to act as a suitable ultrasonic transmission element. Toplace the end effector 478 in the extended configuration the foldedelement 482 is extended in the direction indicated by arrow 490 a by anysuitable techniques. In the illustrated embodiment the folded element482 is configured as a cylindrical element. The cylindrical foldedelement 482 may be slid forwardly toward the distal end. Severalmechanisms may be employed to slide the folded element 482. In oneembodiment, the folded element 482 may be configured with a malethreaded portion at a proximal end to engage a matching female threadedportion formed in the distal end of the 478. Once the folded element 482is located either in the retracted or extended configurations, thefolded element 482 is “locked” into position with sufficient force forsuitable transmission of the ultrasonic energy to either the distal end488 in the extended configuration or the acoustic distal end 489 in theretracted configuration. Additional mechanisms may be included to slidean exterior sheath to protect the tissue from the vibration in theproximal two quarter wavelength segments and expose the tissue to thedistal quarter wavelength. Likewise a mechanism may be provided to slidethe symmetric clamp arm/pad assemblies 452, 462 (FIGS. 9, 10) distallyto be used with only the distal quarter wavelength.

In the retracted configuration (shown in phantom), the extendable endeffector 478 has a physical length L1 of two quarter wavelengths (2λ/4).In the extended configuration, the end effector 478 has a physicallength of approximately two quarter wavelength (2λ/4) and the foldedelement 482 has a length L3 of approximately one quarter wavelength(λ/4). The folded element 482 forms the distal quarter wavelength (λ/4)of the end effector 478. In the extended configuration, the combinedlength of the end effector 478 and the folded element 482 has a physicallength L2 of approximately three quarter wavelengths (3λ/4). The foldedelement 482 may be formed as a solid rod with approximately the samelongitudinal cross-sectional area as the cross-sectional area of thetubular end effector 478 spanning the parallel acoustic path 487. Itwill be appreciated that the end effector 478 may have a physical lengththat is an integer multiple of one quarter wavelength (nλ/4; where “n”is any positive integer; e.g., n=1, 2, 3 . . . ). Similarly, the foldedelement 482 may have a physical length that is an integer multiple ofone quarter wavelength (nλ/4; where “n” is any positive integer; e.g.,n=1, 2, 3 . . . ). The embodiments are not limited in this context.

In the retracted configuration, shown in phantom, the distal end 486coincides with the second node N2. Thus, in the retracted configuration,the free distal end 486 at the node N2 portion of the end effector 478has nominally zero displacement and provides a dull surface to avoiddamage to neighboring tissues when use the active length of 480.

In the extended configuration, the folded element 482 extends from thesecond node N2 to the second antinode A2. A distal end 488 of the foldedelement 482 is a region of maximum amplitude displacement coincidingwith the second antinode A2. In the extended mode, the distal end 488may be used to create a surgical window, -otomy, or back-cutting. Thefolded element 482 may be retracted in the direction indicated by arrow490 b by any suitable techniques. In the retracted configuration (shownin phantom), the folded element 482 is slideably located into a hollowportion 483 of the end effector 478. In the retracted configuration, theend effector 478 comprises an acoustic distal end 489 located at thefirst antinode A1 in terms of displacement and defines a parallelacoustic path 487 with an outer surface of the body 480 of the endeffector 478. In the illustrated embodiment, the parallel acoustic path487 extends between the first antinode A1 and the second node N2. Theacoustic distal end 489 is a region of maximum amplitude displacement.Because the acoustic distal end 489 is located within the hollow portion483, unintended contact with adjacent tissue at high amplitude isavoided.

In the extended configuration, the distal end 488 may be suitable forother surgical procedures such as creating surgical windows, -otomies,and/or back-cutting. During a back-cutting procedure, the surgeon mayemploy the distal end 488 active tip of the end effector 478 to dividetissues along planes.

The proximal end 484 of the extendable end effector 478 is configured tocouple to the velocity transformer 28 at the surface 30 as shown inFIGS. 1 and 2A, for example. The proximal end 484 may be connected to ormay form a portion of an additional transmission waveguide extendingfurther in the proximal direction. For direct connection to the velocitytransformer 28, the end effector 478 may be extended proximally by onequarter wavelength (λ/4) so that the proximal end 484 coincides with anantinode. Accordingly, the velocity transformer 28 and the end effector478 may be joined together at their respective antinodes and the systemfrequency remains near the desired nominal value. In one embodiment, thenominal frequency is 55.5 kHz, for example. The added proximal quarterwavelength may have the same area as the outside parallel path (i.e.,extended proximally by a quarter wavelength). In which case, there is nogain. If the proximal segment has an increased area, then there will beamplitude gain due to the decrease in area with respect to 478 thisrepresents. The end effector 478 may include gain, attenuation, andother features to achieve a desired performance. In the retractedconfiguration, the end effector 478 comprises a free distal end 486 thatcoincides at the second node N2 in terms of amplitude displacement. Thedistal end 486 is a region of minimum amplitude where the longitudinalultrasonic vibration and the ultrasonic displacement is at a minimum. Inthe extended configuration, the extendable end effector 478 alsocomprises a distal end 488 located at a second antinode A2. The distalend 488 is therefore a region of maximum amplitude where thelongitudinal ultrasonic vibration and the ultrasonic displacement is ata maximum. Accordingly, the distal end 488 of the folded element 482 maybe employed to effect tissue.

In other embodiments, the folded element 482 may be folded at adisplacement region located between a node “N” and an antinode “A” suchthat the ultrasonic displacement of the acoustic distal end 488 may bephased between maximum displacement and minimum displacement as shownbelow in FIG. 20. The length of the folded parallel path 707 shown inFIG. 20 is greater than a quarter wavelength (>λ/4).

Yet in other embodiments, the physical length of the folded element 482may be less that one quarter wavelength (λ/4), or less than an integermultiple thereof (nλ/4), such that the ultrasonic displacement of thedistal end 488 is phased between maximum displacement and minimumdisplacement when the folded element 482 is retracted. The combinedlength L2 of the end effector 478 and the extended folded element 482may be any suitable number of wavelengths (λ).

As previously discussed with reference to FIGS. 5, 5A, 5B, at thelocation of the “fold” the extendable end effector 478 retains theultrasonic displacement characteristics of that location without thefold. For example, as shown in FIG. 11, the fold is located at thesecond node N2 and the folded element 482 is extendable one quarterwavelength (λ/4) from the distal end 486 coinciding with the second nodeN2 to the extended distal end 488 coinciding with the second antinodeA2. In the retracted configuration, the second node N2 remains thesecond node N2 and “presents” a free-end.

FIG. 12 illustrates a schematic diagram of one embodiment of a rotatableend effector 500. In one embodiment, the extendable end effector 500 issuitable for use in the embodiment of the single-element end effectorultrasonic system 10 shown in FIG. 1. In another embodiment, the endeffector 500 may be suitably adapted for use in the embodiment of themulti-element end effector system 1000. The end effector 500 comprises abody 501 having a proximal end 504 and a distal end 506 and a foldedelement 502 rotatably coupled to the body 501. In the illustratedembodiment, the end effector 500 is a slotted rectangular bar thatcomprises a solid elongated element 512 and a slot 519 formed at thedistal end. The folded element 502 is rotatably moveable about a pivotaxis 510 at a distal end 506 of the elongated element 512. To locate theend effector 500 in the extended configuration the folded element 502may be rotated outwardly about the axis 510 in the direction indicatedby arrow 514 a. In the extended configuration the folded element 502extends from the second node N2 to the second antinode A2 and behaves asa conventional ultrasonic instrument with maximum ultrasonicdisplacement occurring at the distal end 508 coinciding with the secondantinode A2. To locate the end effector 500 in the retractedconfiguration (shown in phantom) the folded element 502 may be rotatedinwardly about the axis 510 in the direction indicated by arrow 514 b.In the retracted configuration, the distal end 508 of the end effector500 also behaves as the acoustic distal end 509 located at the firstantinode A1 in terms of displacement and forms a parallel acoustic path517 with an outer surface of the body 501 of the end effector 500. Thedistal end 508 is a region of maximum amplitude where the longitudinalultrasonic vibration and the ultrasonic displacement is at a maximum.The distal end 508 of the folded element 502 may be configured to effecttissue. In one embodiment the pivot axis 510 may be implemented as ahinge mechanism.

FIG. 13 is a schematic diagram of a straight elongated end effector 520.In the illustrated embodiment, the length L4 of the end effector 520 istwo quarter wavelengths (2λ/4). The end effector 520 extends from aproximal end 522 located at a first antinode A1, through a node N1, andends at a second antinode A2 at the distal end 524. The ultrasonicdisplacement curve of the end effector 520 is graphically illustrated inFIG. 16.

FIG. 14 is a schematic diagram of one embodiment of an end effector 530comprising a folded element defining a parallel acoustic path 533. Inthe illustrated embodiment, the end effector 530 may be formed byfolding the straight elongated rod end effector 520 (FIG. 13) at thelocation of the node N1. Thus, in the illustrated embodiment, the endeffector 530 comprises a first element 532 extending from the firstantinode A1 to the node N1 and a folded second element 534 that isfolded back towards the proximal end to define the parallel acousticpath 533. In the illustrated embodiment, the folded second element 534may be substantially parallel with the first element 532 and extendsfrom the node N1 to the second antinode A2. In other embodiments, thefolded second element 534 may not be parallel with the first element532. In other embodiments, the folded second element 534 may extend fromthe node N1 to beyond the second antinode A2. It will be appreciatedthat the length L5 of the end effector 530 may be an integer multiple ofone quarter wavelength (nλ/4; where “n” is any positive integer; e.g.,n=1, 2, 3 . . . ). Similarly, the length of the folded second element534 may be an integer multiple of one quarter wavelength (nλ/4; where“n” is any positive integer; e.g., n=1, 2, 3 . . . ). The proximal end536 may be adapted and configured to couple to the velocity transformer28 at the surface 30 as shown in FIGS. 1 and 2A, for example. The lengthof the proximal end 536 may be extended by additional quarterwavelengths to allow the end effector 530 and the velocity transformer30 to be joined at corresponding antinodes. The proximal end 536 may beconnected to or may form a portion of an additional transmissionwaveguide extending further in the proximal direction. The end effector530 comprises an acoustic distal end 538 that is substantially alignedwith the second antinode A2 and is configured to effect tissue (e.g.,cut and/or coagulate). As illustrated in FIG. 14, the first and secondelements 532, 534 may be coupled by a substantially rigid third member540. The displacement of the first and second elements 532, 534 isreferenced to the proximal end 536 and the acoustic distal end 538.Then, the displacement at x=0, e.g., where the first and secondantinodes A1, A2 are aligned, of the first and second elements 532, 534is substantially equal and opposite. Thus, the first and second elements532, 534 have the same magnitude of ultrasonic displacement along theirlongitudinal lengths but in opposite directions. Accordingly, thephysical length L5 of the end effector 530 is one half the length L4 ofthe elongated end effector 520 (FIG. 13). The ultrasonic displacementcurve of the end effector 530 is graphically illustrated in FIG. 17.

FIG. 15 is a schematic diagram of one embodiment of an end effector 550comprising a folded element 562 defining a parallel acoustic path 556.In the illustrated embodiment, the end effector 550 may be formed byfolding a distal segment of the straight end effector 520 (FIG. 13) atthe location coinciding with the node N1 to define a folded element 552in the form of a hook. Thus, in the illustrated embodiment, the endeffector 550 comprises an elongated portion 554 extending from aproximal end 558 to a first antinode A1 and a folded element 552extending from the first antinode A1 to the node N1. The folded element552 comprises a first element 560 extending from the first antinode A1to the node N1 and a folded second element 562 that extends from thenode N1 to the second antinode A2. The folded second element 562 isfolded back towards the proximal end to form a parallel acoustic path553. The folded second element 562 is substantially parallel with thefirst element 560. The length of the end effector 550 may be an integermultiple of one quarter wavelength (nλ/4; where “n” is any positiveinteger; e.g., n=1, 2, 3 . . . ). Similarly, the lengths of theelongated element 554 and the folded element 556 may be an integermultiple of one quarter wavelength (nλ/4; where “n” is any positiveinteger; e.g., n=1, 2, 3 . . . ). The end effector 550 comprises aproximal end 558 configured to couple to the velocity transformer 28 atthe surface 30 as shown in FIGS. 1 and 2A. The proximal end 558 may beconnected to or may form a portion of an additional transmissionwaveguide extending further in the proximal direction. The end effector550 comprises an acoustic distal end 564 that is located substantiallyaligned with the second antinode A2 and is configured to effect tissue(e.g., cut and/or coagulate) located in an opening 566 defined betweenthe first and second elements 560, 562. As illustrated in FIG. 15, thefolded element 552 or hook may be formed by bending a distal segment ofa straight elongated rod ultrasonic transmission waveguide. Thoseskilled in the art will recognize that the elongated portion 554 and/orthe folded element 552 may incorporate balancing features to minimizetransverse vibration in the proximal elongated portion 554. Examples ofultrasonic surgical instruments with balanced end effector features aredisclosed in U.S. Pat. Nos. 6,283,981 and 6,328,751 and are incorporatedherein by reference in their entirety. If the displacement of each ofthe first and second elements 560, 562 is referenced at location x=0,where the first and second antinodes A1, A2 are aligned, thedisplacement of the first and second elements 560, 562 is substantiallyequal and opposite. Thus, the first and second elements 560, 562 havethe same ultrasonic displacement magnitude along their longitudinallengths but in opposite directions. Accordingly, the physical length ofthe folded element 552 of the end effector 550 has twice thedisplacement across the tissue and therefore twice the effectivevelocity and therefore greater heating.

In the embodiment illustrated in FIG. 15, tissue may be located in theopening 566 defined between the first and second elements 560, 562. Thelength of the opening 566 may be one quarter wavelength (λ/4) or may beany integer multiple “n” of one quarter wavelength ((nλ/2; where “n” isany positive integer; e.g., n=1, 2, 3 . . . ). In operation, the foldedelement 552 may be pulled through a portion of tissue to continuouslytransect and coagulate the tissue. In one embodiment, the folded element552 may be employed as a fixed blade such as for mesentery takedown, forexample. In such an embodiment, the first element 560 and the secondelement 562 may be located at a predetermined angle relative to eachother at a distal end 568. The angled feature may be suitable toincrease the nip pressure as the tissue is forced towards the node N1 atthe distal end 568 during a transecting and coagulating procedure. Inanother embodiment, the folded portion 552 may be employed as a shear.In such an embodiment, however, the relative ultrasonic displacementamplitudes of each of the first and second elements 560, 562 may beadjusted to minimize any deleterious effects that may arise if the firstand second elements 560, 562 come into physical metal-to-metal contact.In another implementation of the shears embodiment, the first and secondelements 560, 562 may be formed with a relatively thin coating (e.g.,polymeric, metallic, or oxide) to eliminate or minimize the directmetal-to-metal contact between the first and second elements 560, 562. Amechanism may be coupled to the distal end 568 to apply a squeezingforce to flex the first and second elements 560, 562 such that they actin a shearing mode. In such an implementation, the first and secondelements 560, 562 may be configured as the individual jaws that may beclosed during the transacting process while still transmittingultrasonic energy.

FIG. 16 graphically illustrates a characteristic ultrasonic displacementcurve 570 of the straight elongated end effector 520 shown in FIG. 13.Displacement in terms of ultrasonic amplitude is shown along thevertical axis and the number of quarter wavelengths is shown along thehorizontal axis. The displacement curve 570 amplitude at the firstantinode A1 is +1 (+100%), meaning that the first antinode A1 is alocation of maximum or peak ultrasonic displacement. The displacementamplitude decreases approaching the node N1 and at the node N1, thedisplacement curve 570 amplitude is zero. The displacement curve 570amplitude increases toward a negative maximum displacement approachingthe second antinode A2 and at the second antinode A2 the amplitude ofthe displacement curve 570 is −1 (−100%), meaning that the antinode A2is a location of a negative maximum or peak ultrasonic displacement. Thefirst antinode A1 is located at zero quarter wavelengths or at theproximal end 522 (FIG. 13), the node N1 is located at one quarterwavelength (λ/4) from the proximal end 522, and the second antinode A2is located at two quarter wavelengths (2λ/4) from the proximal end 522.The active length 572 of the end effector 520 is approximately 0.65quarter wavelengths. The active length 574 from the second antinode A2to the displacement curve 570 at the 50% negative also is about 0.65quarter wavelengths.

FIG. 17 graphically illustrates a characteristic ultrasonic displacementcurve 580 of one embodiment of the end effector 530 comprising a foldedelement defining a parallel acoustic path 533 shown in FIG. 14. Thecurve 580 also applies to the other folded end effector embodimentsshown in FIGS. 4, 5, and 6 and starting at their respective A1antinodes. Displacement in terms of ultrasonic amplitude is shown alongthe vertical axis and the number of quarter wavelengths is shown alongthe horizontal axis. The displacement curve 580 amplitude at the firstantinode A1 is +1 (+100%), meaning that the first antinode A1 is alocation of maximum or peak ultrasonic displacement. The displacementamplitude decreases approaching the node N1. The displacement amplitudeat the node N1 is zero. The displacement curve 580 amplitude increasestoward a negative maximum displacement approaching the second antinodeA2 and at the second antinode A2 the amplitude of the displacement curve580 is −1 (−100%), meaning that the first antinode A1 is a location of anegative maximum or peak ultrasonic displacement. The first and secondantinodes A1, A2 are located at the proximal end 536 and the node N1 islocated at one quarter wavelength (λ/4) from the proximal end 536. Theactive length of the end effector 530 remains a nominal 0.65 of awavelength. Both segments, 582, 584, however, have active lengths thatact on tissue captured therebetween. Their active lengths, however, havedisplacements moving in opposite directions so the velocity across thetissue is essentially doubled and therefore thermal energy delivered tothe tissue is doubled.

FIG. 18 is a schematic diagram of one embodiment of an end effector 600comprising a folded element 602 defining a parallel acoustic path 607.In the illustrated embodiment, the fold is located just prior to wherethe distal node N2 would be located. FIG. 18A is a cross-sectional viewof the end effector 600 shown in FIG. 18 taken along line 18A-18A. Inone embodiment, the end effector 600 is suitable for use in theembodiment of the single-element end effector ultrasonic system 10 shownin FIG. 1. In another embodiment, the end effector 600 may be suitablyadapted for use in the embodiment of the multi-element end effectorsystem 1000 shown in FIG. 2A. The end effector 600 comprises a body 609having a proximal end 604 and a distal end 606 and a folded element 602coupled to the body 609. With referred now to FIGS. 18 and 18A, in oneembodiment, the folded element 602 originates at a displacement regionN′ located between a node “N” and an antinode “A” extends beyond a firstantinode A1 and terminates at an acoustic distal end 608, whichcoincides with a second antinode A2. The ultrasonic displacement of theacoustic distal end 608 may be phased between maximum displacement andminimum displacement by suitably locating the acoustic distal end 608 ata predetermined distance from the distal end 606. The end effector 600comprises a proximal end 604 and a distal end 606. The folded element602 originates at the distal end 606, which coincides with thedisplacement region N′ located between the first antinode A1 and thesecond node N2. In the illustrated embodiment, N′ is located at adistance that is less than one quarter wavelength (λ/4) from the secondnode N2. The folded element 602 extends from the distal end 606 parallelto the longitudinal axis B proximally towards the proximal end 604 to aregion beyond the first antinode A1 to a second (e.g., folded) antinodeA2. An outer surface of the body 609 of the distal portion of the endeffector 600 and the folded element 602 define a parallel acoustic path607. It will be appreciated that the length of the parallel acousticpath 607 is substantially the same as the length of the folded element602. The second antinode A2 is shown merely to illustrate the locationof the acoustic distal end 608. In the illustrated embodiment, thelength L′ of the end effector 600 has a physical length, which is lessthan two quarter wavelengths (L′<2λ/4). In the illustrated embodiment,the length of the folded element 602 is greater than one quarterwavelength (>λ/4). The folded element 602 may be formed as a solid rodforming the distal quarter wavelength of the end effector 600. It willbe appreciated that the length of the end effector 600 may be an integermultiple of one quarter wavelength (nλ/4; where “n” is any positiveinteger; e.g., n=1, 2, 3 . . . ). Similarly, the folded element 602 mayhave a physical length that is an integer multiple of one quarterwavelength (nλ/4; where “n” is any positive integer; e.g., n=1, 2, 3 . .. ).

The proximal end 604 of the end effector 600 may be adapted andconfigured to couple to the velocity transformer 28 at the surface 30 asshown in FIGS. 1 and 2A, for example. For direct connection to thevelocity transformer 28, the end effector 600 may be extended proximallyby one quarter wavelength (λ/4) so that the proximal end 604 coincideswith an antinode. Accordingly, the velocity transformer 28 and the endeffector 600 may be joined together at their respective antinodes andthe system frequency remains near the desired nominal value. In oneembodiment, the nominal frequency is 55.5 kHz, for example. The addedproximal quarter wavelength may have the same area as the outsideparallel path (i.e., extended proximally by a quarter wavelength). Inwhich case, there is no gain. If the proximal segment has an increasedarea, then there will be amplitude gain due to the decrease in area withrespect to 600. The end effector 600 may include gain, attenuation, andother features to achieve a desired performance. The proximal end 604may be connected to or may form a portion of an additional transmissionwaveguide extending further in the proximal direction. The end effector600 may include gain, attenuation, and/or other features to achieve adesired performance. The distal end 606 of the end effector 600 is aregion where the displacements of the external and the internal parallelacoustic paths are equal. In the illustrated embodiment, the fold at N′may be selected to coincide with a 50% amplitude point. At the distaltip 606 the slopes of the displacement curve (FIG. 19) are opposite.Accordingly, the stresses are equal and opposite and there is stressequilibrium. The acoustic distal end 608 is located at the secondantinode A2 in terms of displacement and is referred to as the FoldedAntinode A2 in FIG. 19. The acoustic distal end 608 is therefore aregion at a local negative maximum amplitude where the ultrasonicdisplacement of the longitudinal ultrasonic vibration is near a negativemaximum.

In various embodiments, the length of the folded element 602 may begreater than or less than one quarter wavelength (λ/4), or may be lessthan an integer multiple thereof (nλ/4), such that the ultrasonicdisplacement of the acoustic distal end 608 may be phased betweenmaximum displacement and minimum displacement depending on the locationof the acoustic distal end 608 and the overall length of the foldedelement 602. The length of the end effector 600 and the folded element602 may be any suitable number of quarter wavelengths (λ/4). Aparticularly beneficial position for the fold (N′) is at the 50%amplitude level between the first antinode A1 and the second node N2.This means that the distal end 606 will be at the limit of the activelength at the minimum effective amplitude to produce desired tissueeffects. The amplitude remains above the minimum effective amplitudeproximally beyond the first antinode A1. Going further proximallytowards the first node N1, the amplitude falls below the desired levelof 50%. This means the active length (L_(A) shown in FIG. 19) extends tothe distal end back to 1.2 inches (≈30 mm) for end effectors designedwith titanium operating at 55.5 kHz.

The location of the “fold” at N′ along the longitudinal extension of theend effector 600 retains the ultrasonic displacement characteristics ofthat location prior to the fold. For example, in FIG. 18, the fold inthe end effector 600 is located at N′ between the first antinode A1 andthe second node N2 and the solid rod folded element 602 extends onequarter wavelength (λ/4) from the distal end 606 to the acoustic distalend 608 located at the second antinode A2 just beyond the first antinodeA1. The solid rod folded element 602 has the same longitudinalcross-sectional area as the longitudinal cross-sectional area of the endeffector 600 spanning between the fold N′ and the second antinode A2.The displacement at the fold N′ is positive for the external parallelacoustic path 607 as well as the internal parallel acoustic path.Therefore, the distal end 606 of the end effector 600 is active when itis ultrasonically activated. FIG. 19 graphically illustrates anultrasonic displacement curve 630 of the end effector 600.

FIG. 19 graphically illustrates a characteristic ultrasonic displacementcurve 630 of one embodiment of the end effector 600 shown in FIGS. 18and 18A comprising the folded element 602 defining the parallel acousticpath 607. The ultrasonic amplitude is shown along the vertical axis andquarter wavelength is shown along the horizontal axis. The amplitude ofthe displacement curve 630 is approximately zero at the proximal end604, which is the location of the first node N1. The amplitude of thedisplacement curve 630 at the first antinode A1 is +1 (+100%), meaningthat the first antinode A1 is the location of maximum or peak ultrasonicdisplacement. The first antinode A1 is located one quarter wavelengthfrom the proximal end 604. The amplitude of the displacement curve 630at the second node N2 would be approximately zero. However, the endeffector 600 is folded at the fold N′ just prior to where the secondnode N2 would be located. The second node N2 would be located twoquarter wavelengths (2λ/4) from the proximal end 604. Therefore, theamplitude of the displacement curve 630 at the fold N′ is positive. Inthe embodiment illustrated in FIG. 19, the location of the fold N′ isselected such that the amplitude at the fold N′ is at 50% of maximum.The fold N′ is located at less than one quarter wavelengths (<λ/4) fromthe previous antinode A1. As previously discussed, the active lengthL_(A) of an ultrasonic instrument is generally defined as the distancefrom the distal end of the end effector (where ultrasonic displacementis at a maximum) to a proximal location along the end effector whereultrasonic displacement decreases below a predetermined levelapproaching a node (where ultrasonic displacement is at a minimum). Theactive length 632 (or L_(A)) of the end effector 600 is defined as thedistance from a proximal location 634 a along the external parallelacoustic path where the ultrasonic displacement crosses above the 50% orone half-peak level to a distal location 634 b at the fold N′ at thefree distal end 606 where the ultrasonic displacement crosses below 50%or one half-peak level. For the displacement curve 630 shown in FIG. 19,the active length 632 is approximately 1.3 quarter wavelengths orapproximately 1.2 inches (≈30 mm). The peak displacement of theultrasonic displacement curve 630 occurs at the antinode A1. Itdecreases to either side of the middle approaching the first node N1 andthe fold N′. By way of comparison, the active length of the end effector630 is thus approximately double that of the hollow tube end effector400 shown in FIG. 4.

FIG. 20 illustrates one embodiment of a slotted end effector 700comprising a folded element 702 defining a parallel acoustic path 707.In the illustrated embodiment, the fold is located just prior to themost distal node N2. FIG. 20A illustrates cross-sectional view of theslotted end effector 700 shown in FIG. 20 taken along line 20A-20A. Inone embodiment, the end effector 700 is suitable for use in theembodiment of the single-element end effector ultrasonic system 10 shownin FIG. 1. In another embodiment, the end effector 700 may be suitablyadapted for use in the embodiment of the multi-element end effectorsystem 1000 shown in FIG. 2A. The end effector 700 comprises a body 709having a proximal end 704 and a distal end 706 and a folded element 702coupled to the body 709. With reference to FIGS. 20 and 20A, the foldedelement 702 originates at a displacement region fold N′, extendsproximally, and terminates at an acoustic distal end 708. Thus, thefolded element 702 extends from the distal end 706 at the fold N′ andextends parallel to the longitudinal axis B from the distal end 706proximally towards the proximal end 704 past the first antinode A1 to asecond (e.g., folded) antinode A2. The fold N′ is located at a distanceof less than one-quarter wavelength (λ/4) from the most distal antinodeA1. The end effector 700 comprises a proximal end 704 and a distal end706. An outer surface of the body 709 of the distal portion of the endeffector 700 and the folded element 702 define a parallel acoustic path707. The second antinode A2 is shown merely to illustrate the locationof the second antinode A2. In the illustrated embodiment, the length L′of the end effector 700 is less than two quarter wavelengths (L′<2λ/4).The end effector 700 comprises a solid proximal portion 712 and aslotted portion 710 formed at the distal portion. The slotted portion710 defines the folded element 702. The length of the folded element 702is approximately one quarter wavelength (λ4). The folded element 702 maybe a solid rod with the same cross-sectional area as the totalcross-sectional defined by portions 702 a and 702 b of the end effector700. The folded element 702 forms the distal quarter wavelength (λ4) ofthe end effector 700. It will be appreciated that the length of the endeffector 700 may be an integer multiple of one quarter wavelength (nλ/4;where “n” is any positive integer; e.g., n=1, 2, 3 . . . ). Similarly,the length of the folded element 702 may be an integer multiple of onequarter wavelength (nλ/4; where “n” is any positive integer; e.g., n=1,2, 3 . . . ).

The end effector 700 comprises a proximal end 704 that is configured tocouple to the velocity transformer 28 at the surface 30 as shown inFIGS. 1 and 2A, for example. For direct connection to the velocitytransformer 28, the end effector 700 may be extended proximally by onequarter wavelength (λ/4) so that the proximal end 704 coincides with anantinode. Accordingly, the velocity transformer 28 and the end effector700 may be joined together at their respective antinodes and the systemfrequency remains near the desired nominal value. In one embodiment, thenominal frequency is 55.5 kHz, for example. The added proximal quarterwavelength may have the same area as the outside parallel path (i.e.,extended proximally by a quarter wave length). In which case, there isno gain. If the proximal segment has an increased area, then there willbe amplitude gain due to the decrease in area with respect to 700. Theend effector 700 may include gain, attenuation, and other features toachieve a desired performance. The proximal end 704 may be connected toor may form a portion of an additional transmission waveguide extendingfurther in the proximal direction. The distal end 706 of the endeffector 700 is a region where the displacements of the external and theinternal parallel acoustic paths are equal. The proximal end 704 may beconnected to or may form a portion of an additional transmissionwaveguide extending further in the proximal direction. The folded endeffector 700 may include gain, attenuation, and other features toachieve a desired performance of an ultrasonic surgical instrument. Theend effector 700 comprises a free distal end 706, such as a blade tip,that coincides with the fold N′, which is less than one-quarterwavelength (λ/4) distance from the most proximal antinode A1. The distalend 706 is therefore a region where the displacements of the externaland the internal parallel acoustic paths are both positive. Inembodiment, the fold N′ may be selected to coincide with a 50% amplitudepoint. At the distal tip 706 the slopes of the displacement curve(similar to the displacement curve shown in FIG. 19) are opposite.Accordingly, the stresses are equal and opposite and there is stressequilibrium. The end effector 700 also comprises an acoustic distal end708 located at the second antinode A2 in terms of displacement and isreferred to as the Folded Antinode A2. The acoustic distal end 708 istherefore a region near a local negative maximum amplitude where thelongitudinal ultrasonic vibration and the ultrasonic displacement isnear a negative maximum.

In various embodiments, the length of the folded element 702 may begreater than or less than one quarter wavelength (λ/4), or less than aninteger multiple thereof (nλ/4), such that the ultrasonic displacementof the acoustic distal end 708 may be phased between maximumdisplacement and minimum displacement based on the location of theacoustic distal end 708 and the length of the folded element 702. Thelength of the slotted portion 710 may be greater than or less than anynumber of quarter wavelengths (λ/4). Yet together, the total length ofthe end effector 700 and the folded element 702 may be any suitablenumber of quarter wavelengths. A particularly beneficial position forthe fold is at the 50% amplitude level between the first antinode A1 andthe second node N2 at the fold N′. This means that the distal end 706will be at the limit of amplitude to produce desired tissue effects. Theamplitude remains above the minimum effective amplitude proximallybeyond the first antinode A1. Proximally approaching the first node N1,the amplitude falls below the desired level of 50%. This means theactive length extends to the distal end back to 1.3 wavelengths or 1.2inches (≈30 mm) for end effectors designed with titanium operating at55.5 kHz.

The location of the fold N′ along the longitudinal extension of the endeffector 700 retains the ultrasonic displacement characteristics of thatlocation prior to the fold. For example, in FIG. 20, the fold N′ islocated at less than one quarter wavelength (λ/4) from the firstantinode A1. As shown in FIG. 19, the displacement at the fold N′ ispositive for the external parallel acoustic path 707 as well as theinternal parallel acoustic path. Therefore, the distal end 706 of theinstrument is active when it is ultrasonically activated.

FIG. 21A illustrates one embodiment of a multi-element slotted endeffector 800 comprising a folded element 812 defining a parallelacoustic path 807. The end effector 800 comprises a folded element 812having an acoustic distal end 802. In the illustrated embodiment, thefold is located just prior to the most distal node. The fold N′ islocated at less than one quarter wavelengths (<λ/4) from the previousantinode, as described above with respect to FIGS. 19 and 20. Thelocation of the fold N′ is selected such that the amplitude at the foldN′ is at 50% of maximum. The end effector 800 is suitable to formmultiple seal zones in tissue clamped between a clamp pad assembly andsealing elements portions of the end effector 800.

FIG. 21B illustrates schematically a side view of the end effector 800operatively coupled to a clamp arm 804. The clamp arm 804 is adapted toreceive a tissue pad 806. As previously described, the clamp am804/tissue pad 806 assembly (clamp arm assembly) may be configured toapply a compressive or biasing force to the tissue to achieve fastercoagulation (e.g., sealing) and cutting of the tissue. The clamp arm 804is pivotally mounted about a pivot pin (not shown) to rotate to an openposition to receive tissue between the clamp arm 804 and the endeffector 800. The clamp arm 804 and tissue pad 806 are configured tocreate a predetermined force distribution profile along the length(preferably along the active length of the end effector 800) of theclamp arm 804.

FIG. 21C illustrates schematically a side view of one embodiment of theend effector 800 operatively coupled to the clamp arm 804 with a sectionof tissue 808 located between the clamp arm 804 and the end effector800. The tissue 808 is compressed between the clamp arm 804 and the endeffector 800. The tissue 808 is sealed by activating the end effector800 with ultrasonic energy.

FIG. 21D illustrates schematically a top view of one embodiment of theend effector 800 with tissue sealing zones formed along sealing surfaces810 a and 810 b of the end effector 800. In the embodiment illustratedin FIG. 21D, the clamp arm 804 is not shown for clarity. The tissuesealing zones are formed between the sealing elements 810 a, 810 b andthe tissue pad 806. The width of the folded element 812 is selected suchthat the tissue 808 is compressed by the tissue pad 806 between thesealing edges 810 a, 810 b and the tissue pad 806 and is not compressedin the center portion between the sealing edges 810 a, 810 b. Once thetissue 808 is compressed between the sealing edges 810 a, 810 b and thetissue pad 806, the end effector 800 is ultrasonically energized to formtissue sealing zones along the sealing edges 810 a, 810 b. The heatenergy generated by the end effector 800/tissue pad 806 combination istransferred to the tissue 808 along the sealing edges 810 a, 810 bleaving the center portion of the tissue 808 along a cut line Cunsealed. Once the tissue sealing zones are formed along the sealingedges 810 a, 810 b, a knife may be used to cut the unsealed tissue 808along cut line C.

The performance of the folded end effectors have been discussed in termsof the physics governing longitudinal plane wave propagation. Thoseskilled in the art will recognize that the presence of the fold willintroduce shear stresses in the region of the fold. Therefore thenominal displacement at the free-end discussed in embodiments aboverepresents an average value across the distal face of the end effector.

The incorporation of balance features has been discussed in reference tothe end effector 550 of FIG. 15. Balance features can be incorporated inany portion of the folded end effectors as may be necessary to lessenthe undesirable transverse motion.

It is to be understood that any of the embodiments of the ultrasonictransmission waveguides and/or end effectors described herein may beformed as tubular or solid members (e.g., rods, bars) with circular,rectangular, square, triangular, or other suitable polygonalcross-section. The ultrasonic transmission waveguides and/or endeffectors may be formed with either straight or tapered edges toamplify, attenuate, or transmit the amplitude of the vibrations producedby the piezoelectric or magnetostrictive actuators. Furthermore, thefolded elements may be formed as tubular or solid members (e.g., rods,bars) with circular, rectangular, square, triangular, or other suitablepolygonal cross-section. The folded elements may be formed with eitherstraight or tapered edges to amplify, attenuate, or transmit theamplitude of the vibrations produced by the piezoelectric ormagnetostrictive actuators. The embodiments are not limited in thiscontext.

With reference to any of the embodiments previously discussed,ultrasonic instruments may comprise two or more active ultrasonic endeffectors to capture tissue between multiple active end effectors. Forexample, in one embodiment an instrument may comprise two activeultrasonic end effectors to capture tissue between two end effectorelements with substantially equal and opposite ultrasonic displacement.In such embodiment, twice the power may be delivered to the tissue andthe power may be symmetric with respect to the center of the tissue.This latter feature may improve seal strength and enable ultrasonicanastomoses. End effectors comprising folded elements as discussed abovemay be employed to achieve twice the active length. A folded element mayexhibit ultrasonic displacement in a direct segment and oppositedisplacement in a parallel segment to achieve double active endeffectors. A folded resonant element may be configured such that adistal segment is folded at a displacement node N. At the location ofthe fold, the distal end of the folded resonant element is a free endthat remains a node N after it is folded. The acoustic distal end of thefolded segment, however, is active and is located at an antinode A.

With reference to any of the embodiments previously discussed, it willbe appreciated that in other embodiments, the folded element (e.g.,folded rod ultrasonic end effector and the folded blade portion) may becoupled to a displacement region located between a node “N” and anantinode “A” such that the ultrasonic displacement of the acousticelements may be phased between maximum displacement and minimumdisplacement. Yet in other embodiments, the physical length of thefolded element may be less that one quarter wavelength (λ/4), or lessthan an integer multiple thereof (nλ/4), such that the ultrasonicdisplacement of the distal end is phased between maximum displacementand minimum displacement. In addition, the length of the straightportion of the folded ultrasonic transmission waveguide may be anysuitable number of wavelengths (λ).

With reference to FIGS. 2A-D, 9, 10, and 21A-D that illustrate variousembodiments comprising multi-element end effectors and clamp armassemblies comprising proximal tissue pad segments, distal tissue padsegments, and tissue pad insert segments. The pivotal movement of theclamp arm assemblies with respect to the blades may be affected by theprovision of a pair of pivot points on the clamp arm portion of theclamp arm assembly that interfaces with an ultrasonic surgicalinstrument via weld pin fastening or other fastening means (not shown).The tissue pad segments may be attached to the clamp arm by mechanicalmeans including, for example, rivets, glues, adhesives, epoxies, pressfitting or any other fastening techniques known in the art. Furthermore,the tissue pad segments may be removably attached to the clamp arm byany known techniques.

In various embodiments, the clamp arm may comprise a T-shaped slot foraccepting a T-shaped flange of a tissue pad (e.g., the tissue pads 806,1021 described herein). In various embodiments, a single unitary tissuepad assembly may comprise the tissue pad segment and further comprises aT-shaped flange for reception in a T-shaped slot in the clamp armassembly. Additional configurations including dove tailed-shaped slotsand wedge-shaped flanges are contemplated. As would be appreciated bythose skilled in the art, flanges and corresponding slots havealternative shapes and sizes to removably secure the tissue pad to theclamp arm.

The devices disclosed herein can be designed to be disposed of after asingle use, or they can be designed to be used multiple times. In eithercase, however, the devices can be reconditioned for reuse after at leastone use. Reconditioning can include any combination of the steps ofdisassembly of the device, followed by cleaning or replacement ofparticular pieces, and subsequent reassembly. In particular, the devicecan be disassembled, and any number of the particular pieces or parts ofthe device can be selectively replaced or removed in any combination.Upon cleaning and/or replacement of particular parts, the device can bereassembled for subsequent use either at a reconditioning facility, orby a surgical team immediately prior to a surgical procedure. Thoseskilled in the art will appreciate that reconditioning of a device canutilize a variety of techniques for disassembly, cleaning/replacement,and reassembly. Use of such techniques, and the resulting reconditioneddevice, are all within the scope of the present application.

Preferably, the various embodiments of the devices described herein willbe processed before surgery. First, a new or used instrument is obtainedand if necessary cleaned. The instrument can then be sterilized. In onesterilization technique, the instrument is placed in a closed and sealedcontainer, such as a plastic or TYVEK® bag. The container and instrumentare then placed in a field of radiation that can penetrate thecontainer, such as gamma radiation, x-rays, or high-energy electrons.The radiation kills bacteria on the instrument and in the container. Thesterilized instrument can then be stored in the sterile container. Thesealed container keeps the instrument sterile until it is opened in themedical facility.

It is preferred that the device is sterilized. This can be done by anynumber of ways known to those skilled in the art including beta or gammaradiation, ethylene oxide, steam.

Although various embodiments have been described herein, manymodifications and variations to those embodiments may be implemented.For example, different types of end effectors may be employed. Also,where materials are disclosed for certain components, other materialsmay be used. The foregoing description and following claims are intendedto cover all such modification and variations.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

1. An end effector for use with an ultrasonic surgical instrument,comprising: a body extending along a longitudinal axis comprising aproximal end and a distal end, the body comprising an outer surface thatdefines an inner portion, the proximal end of the body is configured tocouple to an ultrasonic transducer configured to produce vibrations at apredetermined frequency and a predetermined amplitude; a folded elementhaving a predetermined length, the folded element comprising a first endcoupled to the distal end of the body and extending proximally along thelongitudinal axis from the distal end of the body toward the proximalend of the body into the inner portion, the folded element comprising asecond free acoustic end; wherein the folded element and the outersurface of the body define a single substantially parallel acoustic pathspanning the length of the folded element; and a clamp arm operativelycoupled to the body.
 2. The end effector of claim 1, wherein the distalend of the body substantially coincides with a node, wherein the node isa location of minimum amplitude displacement, wherein the second freeacoustic end of the folded element substantially coincides with anantinode, wherein the antinode is a location of maximum amplitudedisplacement, and wherein when the end effector is energized by theultrasonic transducer, the distal end of the body substantiallycoinciding with the node remains stable and the second free acoustic endvibrates at the predetermined frequency and amplitude
 3. The endeffector of claim 1, comprising a tissue pad coupled to the clamp arm.4. The end effector of claim 1, wherein the clamp arm is configured toapply a predetermined force profile against the body, wherein the forceis inversely proportional to a displacement profile of the active lengthof the body.
 5. The end effector of claim 4, wherein the clamp arm isconfigured as a leaf-spring.
 6. The end effector of claim 4, wherein theclamp arm comprises a spring operatively coupled to first and secondhinged clamp arm members.
 7. The end effector of claim 1, wherein thedistal end of the body is located in proximity to a node; and whereinthe second free acoustic end of the folded element is located inproximity to an antinode.
 8. The end effector of claim 1, wherein thedistal end of the body substantially coincides with a first displacementregion located between a node and an antinode; and wherein the secondfree acoustic end of the folded element substantially coincides with asecond displacement region located between a node and an antinode. 9.The end effector of claim 1, wherein the body is configured as a tubularmember and the folded element is configured as a solid member.
 10. Theend effector of claim 1, wherein the body comprises a solid portion atthe proximal end and a hollow portion at the distal end, wherein thehollow portion defines a slot to receive the folded element therein. 11.The end effector of claim 1, wherein the outer surface of the bodydefines an active length that is greater than one quarter wavelength,wherein the active length is defined as a region that begins at thedistal end of the body where amplitude displacement is at a minimum andextend proximally to a location where the amplitude displacement isone-half of a maximum amplitude displacement that occurs along theactive length.
 12. The end effector of claim 1, wherein the longitudinalcross-sectional area of the body is substantially equal to thelongitudinal cross-sectional area of the folded element.
 13. A surgicalinstrument, comprising: a transducer configured to produce vibrationsalong a longitudinal axis at a predetermined frequency and apredetermined amplitude; an end effector for use with an ultrasonicsurgical instrument, comprising: a body extending along a longitudinalaxis comprising a proximal end and a distal end, the body comprising anouter surface that defines an inner portion, the proximal end of thebody is configured to couple to an ultrasonic transducer configured toproduce vibrations at a predetermined frequency and a predeterminedamplitude; a folded element having a predetermined length, the foldedelement comprising a first end coupled to the distal end of the body andextending proximally along the longitudinal axis from the distal end ofthe body toward the proximal end of the body into the inner portion, thefolded element comprising a second free acoustic end; wherein the foldedelement and the outer surface of the body define a single substantiallyparallel acoustic path spanning the length of the folded element; and aclamp arm operatively coupled to the body.
 14. The surgical instrumentof claim 13, wherein the folded element comprises sealing edges formedon lateral portions of the body.
 15. The surgical instrument of claim13, wherein the body is configured as a tubular member and the foldedelement is configured as a solid member.
 16. The surgical instrument ofclaim 13, wherein the body comprises a solid portion at the proximal endand a hollow portion at the distal end, wherein the hollow portiondefines a slot to receive the folded element therein.
 17. The surgicalinstrument of claim 13, wherein when the end effector is energized bythe ultrasonic transducer, the outer surface of the body defines anactive length that is greater than one quarter wavelength, wherein theactive length is defined as a region that begins at the distal end ofthe body where amplitude displacement is at a minimum and extendproximally to a location where the amplitude displacement is one-half ofa maximum amplitude displacement that occurs along the active length.18. The surgical instrument of claim 13, wherein the longitudinalcross-sectional area of the body is substantially equal to thelongitudinal cross-sectional area of the folded element.
 19. An endeffector for use with an ultrasonic surgical instrument, comprising: abody extending along a longitudinal axis comprising a proximal end and adistal end, the body comprising an outer surface that defines an innerportion, the proximal end of the body is configured to couple to anultrasonic transducer configured to produce vibrations at apredetermined frequency and a predetermined amplitude; a folded elementhaving a predetermined length, the folded element comprising a first endcoupled to the distal end of the body and extending proximally along thelongitudinal axis folded element comprising a second free acoustic end;wherein the folded element and the outer surface of the body define asingle substantially parallel acoustic path spanning the length of thefolded element, the folded element comprising sealing edges formed onlateral portions of the body; and a clamp arm operatively coupled to thebody.
 20. The end effector of claim 19, comprising a tissue pad coupledto the clamp arm
 21. The end effector of claim 20, wherein the clamp armis configured to apply a predetermined force between the tissue pad andthe sealing edges.
 22. The end effector of claim 19, wherein the body isadapted to receive a knife between the first and second sealing edges.